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IDF Diabetes Atlas: The prevalence of pre-existing diabetes in pregnancy – A systematic reviewand meta-analysis of studies published during 2010–2020

Published:December 06, 2021DOI:https://doi.org/10.1016/j.diabres.2021.109049

      Abstract

      Objectives

      To estimate the prevalence of pre-existing diabetes in pregnancy from studies published during 2010–2020.

      Methods

      We searched PubMed, CINAHL, Scopus and other sources for relevant data sources. The prevalence of overall pre-existing, type 1 and type 2 diabetes, by country, region and period of study was synthesised from included studies using the inverse-variance heterogeneity model and the Freeman-Tukey transformation. Heterogeneity was assessed using the I2 statistic and publication bias using funnel plots.

      Results

      We identified 2479 records, of which 42 data sources with a total of 78 943 376 women, met the eligibility criteria. The included studies were from 17 countries in North America, Europe, the Middle East and North Africa, Australasia, Asia and Africa. The lowest prevalence was in Europe (0.5%, 95 %CI 0.4–0.7) and the highest in the Middle East and North Africa (2.4%, 95 %CI 1.5–3.1). The prevalence of pre-existing diabetes doubled from 0.5% (95 %CI 0.1–1.0) to 1.0% (95 %CI 0.6–1.5) during the period 1990–2020. The pooled prevalences of pre-existing type 1 and type 2 diabetes were 0.3% (95 %CI 0.2–0.4) and 0.2% (95 %CI 0.0–0.9) respectively.

      Conclusion

      While the prevalence of pre-existing diabetes in pregnancy is low, it has doubled from 1990 to 2020.

      Keywords

      Abbreviations:

      T1D (Type 1 diabetes mellitus), T2D (Type 2 diabetes mellitus), GDM (Gestational diabetes mellitus), DIP (Diabetes mellitus in pregnancy), IDF (International Diabetes Federation), pDM (Pre-existing diabetes mellitus), NSW 2019 (Centre for Epidemiology and Evidence. New South Wales Mothers and Babies 2019), AIHW 2010 (Australian Institute of Health and Welfare 2010), NWH 2018 (National Women's Health 2018), NOIS 2018 (National Obstetrics Information System 2015–2019), DPS 2018 (Drugs and Pregnancy study 2018), WHO (World Health Organization)

      1. Introduction

      Hyperglycaemia in pregnancy (HIP), either from pre-existing diabetes, defined as any type of diabetes diagnosed before the index pregnancy, or hyperglycaemia first detected in pregnancy (HFDP), affects about 16% of pregnancies globally [

      International Diabetes Federation. IDF Diabetes Atlas 9th Edition: International Diabetes Federation.; 2019 [cited 2020 13 January]. 9:[Available from: http://www.diabetesatlas.org.

      ]. HFDP, the major contributor to HIP [

      International Diabetes Federation. IDF Diabetes Atlas 9th Edition: International Diabetes Federation.; 2019 [cited 2020 13 January]. 9:[Available from: http://www.diabetesatlas.org.

      ], includes diabetes in pregnancy, where women have blood glucose levels in the range of diabetes outside pregnancy but diagnosed during the pregnancy, and gestational diabetes mellitus [GDM] [

      World Health Organization. Diagnostic criteria and classification of hyperglycaemia first detected in pregnancy 2013 [Available from: https://apps.who.int/iris/bitstream/handle/10665/85975/WHO_NMH_MND_13.2_eng.pdf;jsessionid=48ABC998E153A412E00E1CD62B90C1EC?sequence=1.

      ]. Pre-existing diabetes affects a small proportion of pregnancies, estimated to be less than or around 2% [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ]. However, women with pre-existing diabetes require intensive clinical care and support [
      • Kitzmiller J.L.
      • Block J.M.
      • Brown F.M.
      • Catalano P.M.
      • Conway D.L.
      • Coustan D.R.
      • et al.
      Managing preexisting diabetes for pregnancy: summary of evidence and consensus recommendations for care.
      ] before and during pregnancy to optimise glycaemic control and reduce the risk of diabetes-related pregnancy complications [
      • Mondestin M.A.J.
      • Ananth C.V.
      • Smulian J.C.
      • Vintzileos A.M.
      Birth weight and fetal death in the United States: the effect of maternal diabetes during pregnancy.
      ,
      • Peticca P.
      • Keely E.J.
      • Walker M.C.
      • Yang Q.
      • Bottomley J.
      Pregnancy outcomes in diabetes subtypes: how do they compare? A province-based study of Ontario, 2005–2006.
      ]. Although good glycaemic control during pregnancy reduces the risk of major perinatal complications and congenital abnormalities, women with pre-existing diabetes still have an excess risk of adverse pregnancy outcomes such as foetal death, maternal pre-eclampsia, and congenital malformations [
      • Mondestin M.A.J.
      • Ananth C.V.
      • Smulian J.C.
      • Vintzileos A.M.
      Birth weight and fetal death in the United States: the effect of maternal diabetes during pregnancy.
      ,
      • Peticca P.
      • Keely E.J.
      • Walker M.C.
      • Yang Q.
      • Bottomley J.
      Pregnancy outcomes in diabetes subtypes: how do they compare? A province-based study of Ontario, 2005–2006.
      ,
      • Parimi M.
      • Nitsch D.
      A Systematic Review and Meta-Analysis of Diabetes During Pregnancy and Congenital Genitourinary Abnormalities.
      ]. Aside from the immediate adverse outcomes, pre-existing diabetes in pregnancy is also associated with a higher risk of long-term adverse metabolic outcomes in the offspring such as increased risk of future obesity and glucose intolerance [
      • Kitzmiller J.L.
      • Ferrara A.
      • Peng T.
      • Cissell M.A.
      • Kim C.
      Preexisting Diabetes and Pregnancy.
      ]. Because of the complexity of the care required [
      • Alexopoulos A.S.
      • Blair R.
      • Peters A.L.
      Management of Preexisting Diabetes in Pregnancy: A Review.
      ] and the high risk of complications for both the mother and her offspring, clinical care for women with pre-existing diabetes is usually undertaken at tertiary institutions by multidisciplinary specialist teams and the costs of care are high [
      • Kitzmiller J.L.
      • Block J.M.
      • Brown F.M.
      • Catalano P.M.
      • Conway D.L.
      • Coustan D.R.
      • et al.
      Managing preexisting diabetes for pregnancy: summary of evidence and consensus recommendations for care.
      ]. This represents a big challenge for low-and-middle-income countries [LMIC] [
      • Beran D.
      ]. It is therefore important to have accurate estimates of the prevalence of pre-existing diabetes to help with adequate resource allocation for the care for this group of women.
      Despite the existence of large surveys and birth registers in several high-income countries [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ,
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ,
      • Barrett P.M.
      • McCarthy F.P.
      • Evans M.
      • Kublickas M.
      • Perry I.J.
      • Stenvinkel P.
      • et al.
      Stillbirth is associated with increased risk of long-term maternal renal disease: a nationwide cohort study.
      ] there are no known estimates of the current prevalence of pre-existing diabetes in pregnancy globally. In its annual reports, the International Diabetes Federation [IDF] Atlas [

      International Diabetes Federation. IDF Diabetes Atlas 9th Edition: International Diabetes Federation.; 2019 [cited 2020 13 January]. 9:[Available from: http://www.diabetesatlas.org.

      ] estimates the prevalence of HIP, and in particular, GDM. However, the prevalence of pre-existing diabetes in pregnancy is not usually included, primarily due to the lack of high-quality data from many countries. Given the continued increase in the prevalence of obesity-driven type 2 diabetes [T2D] [

      International Diabetes Federation. IDF Diabetes Atlas 9th Edition: International Diabetes Federation.; 2019 [cited 2020 13 January]. 9:[Available from: http://www.diabetesatlas.org.

      ], the prevalence of pre-existing diabetes in pregnancy is also likely to increase. Data from the USA [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,

      Bardenheier BH, Imperatore G, Devlin HM, Kim SY, Cho P, Geiss LS. Trends in pre-pregnancy diabetes among deliveries in 19 U.S. states, 2000-2010. Am J Prev Med. 2015;48(2):154-61.

      ] and Canada [
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ] suggest that the prevalence of pre-existing diabetes in pregnancy increased in these countries by 2–4-fold during the period 1990–2010. Whether this increase has occurred in all IDF regions is unknown, as data are either lacking or not collated. Unlike the field of GDM where the body of work has grown exponentially during the last two decades, research on pre-existing diabetes in pregnancy is more limited.
      Previously, pre-existing diabetes in pregnancy was mostly due to type 1 diabetes [T1D] with T2D constituting a smaller proportion [
      • Kitzmiller J.L.
      • Ferrara A.
      • Peng T.
      • Cissell M.A.
      • Kim C.
      Preexisting Diabetes and Pregnancy.
      ]. However, this may no longer be the case as T2D is now increasing in the young [
      • Likitmaskul S.
      • Kiattisathavee P.
      • Chaichanwatanakul K.
      • Punnakanta L.
      • Angsusingha K.
      • Tuchinda C.
      Increasing prevalence of type 2 diabetes mellitus in Thai children and adolescents associated with increasing prevalence of obesity.
      ,
      • Kao K.T.
      • Sabin M.A.
      Type 2 diabetes mellitus in children and adolescents.
      ], driven by the growing prevalence of obesity amongst young people [
      • Likitmaskul S.
      • Kiattisathavee P.
      • Chaichanwatanakul K.
      • Punnakanta L.
      • Angsusingha K.
      • Tuchinda C.
      Increasing prevalence of type 2 diabetes mellitus in Thai children and adolescents associated with increasing prevalence of obesity.
      ,
      • Kao K.T.
      • Sabin M.A.
      Type 2 diabetes mellitus in children and adolescents.
      ,
      • Pulgaron E.R.
      • Delamater A.M.
      Obesity and type 2 diabetes in children: epidemiology and treatment.
      ]. Further, more women are becoming pregnant at advanced ages [
      • Kenny L.C.
      • Lavender T.
      • McNamee R.
      • O’Neill S.M.
      • Mills T.
      • Khashan A.S.
      • et al.
      Advanced maternal age and adverse pregnancy outcome: evidence from a large contemporary cohort.
      ,
      • Flenady V.
      • Koopmans L.
      • Middleton P.
      • Frøen J.F.
      • Smith G.C.
      • Gibbons K.
      • et al.
      Major risk factors for stillbirth in high-income countries: a systematic review and meta-analysis.
      ,
      • Laopaiboon M.
      • Lumbiganon P.
      • Intarut N.
      • Mori R.
      • Ganchimeg T.
      • Vogel J.P.
      • et al.
      Advanced maternal age and pregnancy outcomes: a multicountry assessment.
      ] and there may be increased intergenerational transmission of diabetes risk through intrauterine exposure to hyperglycaemia [

      Bunt JC, Tataranni PA, Salbe ADJTJoCE, Metabolism. Intrauterine exposure to diabetes is a determinant of hemoglobin A1c and systolic blood pressure in Pima Indian children. 2005;90(6):3225-9.

      ]. Again, the true estimates of pre-existing T1D and T2D in pregnancy are not well known. This systematic review and meta-analysis aimed to describe the global prevalence of pre-existing diabetes in pregnancy, drawing on studies published from January 2010 to December 2020. Furthermore, we sought to estimate the prevalence of pre-existing diabetes in pregnancy in each of the IDF regions and to examine trends in the prevalence of diabetes throughout this time period.

      2. Methods

      2.1 Study Design and protocol registration

      This study employed a systematic review and meta-analysis design and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis [PRISMA] guidelines [
      • Page M.J.
      • Moher D.
      • Bossuyt P.M.
      • Boutron I.
      • Hoffmann T.C.
      • Mulrow C.D.
      • et al.
      explanation and elaboration: updated guidance and exemplars for reporting systematic reviews.
      ].

      2.2 Search strategy and data sources

      We carried out a comprehensive search for studies in PubMed, CINAHL, Scopus and websites of government and research bodies for data sources, without language or geographical filters. We hand-searched the reference lists of included studies and consulted experts for any additional studies. We searched each data source on the 31st of October 2020 and updated the search on the 19th of January 2021. We limited the search to studies published during the period 1 January 2010 to 31st of December 2020. The detailed electronic search strategy is shown in Supplementary Table 1.

      2.3 Screening of studies for inclusion

      The records of the identified studies across the search databases were exported into COVIDENCE [https://app.covidence.org/], a systematic review management software. Duplicates were removed before screening. Six reviewers screened the studies for preliminary inclusion using the titles and abstracts. Two authors reviewed each study using COVIDENCE. Where conflicts in the selection of studies appeared, consensus was carried out by a third author, independently. Subsequently, two reviewers independently assessed each of the full text of studies eligible for full-text screening. A predefined eligibility criteria checklist was used for the full-text assessment.

      2.4 Eligibility

      Population-based cross-sectional studies or baseline data from representatively sampled cohort studies that assessed the prevalence of pre-existing diabetes in pregnancy were eligible for inclusion in this review. Eligible studies should have been published during the period 1 January 2010 and 31 December 2020. Experimental studies, case studies, case series, duplicate reports, commentaries, and reviews were excluded. Studies that combined the prevalence of diabetes first detected in pregnancy with that of pre-existing diabetes in pregnancy were excluded if they did not report the prevalence of pre-existing diabetes separately.

      2.5 Outcomes

      The primary outcome of this systematic review was the overall prevalence of pre-existing diabetes in pregnancy defined as any diabetes that was diagnosed before the index pregnancy, irrespective of the type of diabetes. A secondary outcome of the review was to describe the prevalence of pre-existing T1D and T2D in pregnancy.

      2.6 Data extraction

      Once all the included studies were identified, two reviewers extracted data from each included study independently. We extracted data on the characteristics of the included studies. This included authors, citation, year of publication, study period, country, setting, whether the study was nationally representative, regionally or single-centre, the study design used, the total participants assessed, total of pre-existing diabetes, total of T1D and T2D. We extracted the same data within age-groups if the authors reported the age-specific data.

      2.7 Assessment of study quality and risk of bias

      We assessed the methodological quality of included studies in terms of internal validity, external validity, response rate, and generalisability of study results. We used the ten-item rating system developed by Hoy and colleagues [
      • Laopaiboon M.
      • Lumbiganon P.
      • Intarut N.
      • Mori R.
      • Ganchimeg T.
      • Vogel J.P.
      • et al.
      Advanced maternal age and pregnancy outcomes: a multicountry assessment.
      ] and modified by Werfalli and colleagues [

      Werfalli M, Musekiwa A, Engel ME, Ross I, Kengne AP, Levitt NSJBo. The prevalence of type 2 diabetes mellitus among older people in Africa: a systematic review study protocol. 2014;4(6):e004747.

      ] [Supplementary document 1] to assess sampling, the sampling frame and size, outcome measurement, outcome assessment, response rate, and statistical reporting. Each item was assigned a score of 1 [yes] or 0 [no], and scores were summed across items to generate an overall quality score that ranged from 0 to 10. Each study was rated as having a low, moderate, or high risk of bias dependent on the number of questions answered as “yes [Low risk]”: studies at low risk of bias had scores higher than 8, moderate a score of 6–8, and high a score of 5 or lower. Risk of selection and attrition biases were assessed according to the Cochrane guidelines, two reviewers [MW and CH] independently assessed study quality, with disagreements being resolved by consensus.

      2.8 Synthesis of findings

      We described the characteristics of the included studies narratively. We used Tableau version 2021.1 [

      Tableau 2021.1. Tableau. 2003-2021 Tableau Software, LLC, a Salesforce Company2021.

      ] software to create maps showing the geographic origin of the included studies and the prevalence in each country. For each study, we recalculated the unadjusted prevalence of each outcome, i.e., overall pre-existing diabetes, T1D and T2D and then used the inverse heterogeneity model [
      • Doi S.A.R.
      • Barendregt J.J.
      • Khan S.
      • Thalib L.
      • Williams G.M.
      Advances in the meta-analysis of heterogeneous clinical trials I: the inverse variance heterogeneity model.
      ] to pool study prevalence by applying the Freeman-Turkey variance stabilising transformation and then back-transforming the prevalence estimates. We pooled prevalence in each country, where sufficient data were available. We also pooled studies by IDF region and by the period during which the study was carried out. We categorised these periods into the periods 1990–2010, 2000–2010, 2011–2020, based on the study periods within the published studies. We reported prevalence and their 95% confidence intervals [95 %CI] and used forest plots to display the findings. We assessed heterogeneity using the I2 statistic and Cochran’s Q statistic and assessed publication bias using funnel plots. We used the metan package in Stata version 15.1 [

      Stata Press. Stata Statistical Software. Stata Corporation, College Station,2016.

      ] for all meta-analyses.

      2.9 Ethics

      Ethical approvals were not required as the review used data from published studies.

      3. Results

      3.1 Search results

      We identified 2483 records from all searches and 2157 records were assessed for inclusion, using the title and abstract only, after the removal of duplicates [Fig. 1]. After exclusion of 1989 irrelevant records, the full texts of 168 studies were screened, and 126 data sources were excluded. The reasons for exclusion are listed in Fig. 1. A total of 42 data sources were finally included.
      Figure thumbnail gr1
      Fig.1PRISMA flow chart Abbreviations: GDM – gestational diabetes, HFDP – hyperglycaemia first detected in pregnancy, pDM – pre-existing diabetes.

      3.2 Characteristics of included studies

      The 42 included studies had a combined total of 78 943 376 women and were from 17 countries and six regions. There were 14 studies from North America, 12 from Europe, five from the Middle East and North Africa, five from Australasia, three from Asia and two from Africa. The USA [8 studies], Canada [5 studies] and Australia [4 studies] contributed most of the studies [Supplementary Table 1]. The two studies from Africa were both from Ethiopia and, from Asia, two studies were from China and one study from India [
      • Kalra B.
      • Kalra S.
      • Choudhary M.
      • Thakral M.
      Prevalence of Pharamcologically-treated Diabetes in Term Pregnancies in Haryana, India.
      ]. For most of the studies [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ,
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ,

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Cynthia P.
      • Timothy S.
      • Isabelle E.
      What is the impact of diabetes for Australian Aboriginal women when pregnant?.
      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Deputy N.P.
      • Kim S.Y.
      • Conrey E.J.
      • Bullard K.M.
      Prevalence and Changes in Preexisting Diabetes and Gestational Diabetes Among Women Who Had a Live Birth - United States, 2012–2016.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,
      • Fong A.
      • Serra A.
      • Herrero T.
      • Pan D.
      • Ogunyemi D.
      Pre-gestational versus gestational diabetes: a population based study on clinical and demographic differences.
      ,
      • Jaffe A.
      • Giveon S.
      • Rubin C.
      • Novikov I.
      • Ziv A.
      • Kalter-Leibovici O.
      Gestational diabetes risk in a multi-ethnic population.
      ,
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • Lai F.Y.
      • Johnson J.A.
      • Dover D.
      • Kaul P.
      Outcomes of singleton and twin pregnancies complicated by pre-existing diabetes and gestational diabetes: A population-based study in Alberta, Canada, 2005–11.
      ,
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • System N.O.I.
      ,
      • Oster R.T.
      • King M.
      • Morrish D.W.
      • Mayan M.J.
      • Toth E.L.
      Diabetes in pregnancy among First Nations women in Alberta, Canada: a retrospective analysis.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ,
      • Soliman A.
      • Salama H.
      • Al Rifai H.
      • De Sanctis V.
      • Al-Obaidly S.
      • Al Qubasi M.
      • et al.
      The effect of different forms of dysglycemia during pregnancy on maternal and fetal outcomes in treated women and comparison with large cohort studies.
      ,
      • Sormunen‐Harju H.
      • Koivusalo S.
      • Gissler M.
      • Metsälä J.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ,

      The Drugs and Pregnancy project. Drugs and pregnancy 2018.

      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,
      • Xiang A.H.
      • Wang X.
      • Martinez M.P.
      • Walthall J.C.
      • Curry E.S.
      • Page K.
      • et al.
      Association of Maternal Diabetes With Autism in Offspring.
      ], the mean ages of included women were between 29 and 31 years, the lowest mean age [25.2 years] was in one study [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ] from China, and the highest mean age in a study [
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ] from Spain [Supplementary Table 1]. The sample sizes ranged from 491 in a study from Ethiopia [
      • Adugna D.G.
      • Enyew E.F.
      • Jemberie M.T.
      Prevalence and Associated Factors of Macrosomia Among Newborns Delivered in University of Gondar Comprehensive Specialized Hospital, Gondar, Ethiopia: An Institution-Based Cross-Sectional Study.
      ] to 43 121 708 in a study from the USA [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ]. Twenty-one of the studies were population-based cohorts [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ,
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ,
      • Barrett P.M.
      • McCarthy F.P.
      • Evans M.
      • Kublickas M.
      • Perry I.J.
      • Stenvinkel P.
      • et al.
      Stillbirth is associated with increased risk of long-term maternal renal disease: a nationwide cohort study.
      ,
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ,

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Deputy N.P.
      • Kim S.Y.
      • Conrey E.J.
      • Bullard K.M.
      Prevalence and Changes in Preexisting Diabetes and Gestational Diabetes Among Women Who Had a Live Birth - United States, 2012–2016.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,
      • Fong A.
      • Serra A.
      • Herrero T.
      • Pan D.
      • Ogunyemi D.
      Pre-gestational versus gestational diabetes: a population based study on clinical and demographic differences.
      ,
      • Lai F.Y.
      • Johnson J.A.
      • Dover D.
      • Kaul P.
      Outcomes of singleton and twin pregnancies complicated by pre-existing diabetes and gestational diabetes: A population-based study in Alberta, Canada, 2005–11.
      ,
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • Oster R.T.
      • King M.
      • Morrish D.W.
      • Mayan M.J.
      • Toth E.L.
      Diabetes in pregnancy among First Nations women in Alberta, Canada: a retrospective analysis.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ,
      • Soliman A.
      • Salama H.
      • Al Rifai H.
      • De Sanctis V.
      • Al-Obaidly S.
      • Al Qubasi M.
      • et al.
      The effect of different forms of dysglycemia during pregnancy on maternal and fetal outcomes in treated women and comparison with large cohort studies.
      ,
      • Sormunen‐Harju H.
      • Koivusalo S.
      • Gissler M.
      • Metsälä J.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ,

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ,

      Australian women and their babies 2010 [Available from: https://www.adips.org/downloads/dip2010-aihw.pdf.

      ]; nine were cohort studies[
      • Cynthia P.
      • Timothy S.
      • Isabelle E.
      What is the impact of diabetes for Australian Aboriginal women when pregnant?.
      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Jaffe A.
      • Giveon S.
      • Rubin C.
      • Novikov I.
      • Ziv A.
      • Kalter-Leibovici O.
      Gestational diabetes risk in a multi-ethnic population.
      ,
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,
      • Xiang A.H.
      • Wang X.
      • Martinez M.P.
      • Walthall J.C.
      • Curry E.S.
      • Page K.
      • et al.
      Association of Maternal Diabetes With Autism in Offspring.
      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ,
      • Wahabi H.
      • Fayed A.
      • Esmaeil S.
      • Mamdouh H.
      • Kotb R.
      Prevalence and Complications of Pregestational and Gestational Diabetes in Saudi Women: Analysis from Riyadh Mother and Baby Cohort Study (RAHMA).
      ]; five were healthcare centre pregnancy records reviews four were cross-sectional studies and the remaining three studies were audits of birth registers[
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,
      • System N.O.I.
      ,

      The Drugs and Pregnancy project. Drugs and pregnancy 2018.

      ]. Thirteen of the studies included women who were pregnant during the period 2000–2010 [
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ,

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Cynthia P.
      • Timothy S.
      • Isabelle E.
      What is the impact of diabetes for Australian Aboriginal women when pregnant?.
      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Fong A.
      • Serra A.
      • Herrero T.
      • Pan D.
      • Ogunyemi D.
      Pre-gestational versus gestational diabetes: a population based study on clinical and demographic differences.
      ,
      • Jaffe A.
      • Giveon S.
      • Rubin C.
      • Novikov I.
      • Ziv A.
      • Kalter-Leibovici O.
      Gestational diabetes risk in a multi-ethnic population.
      ,
      • Lai F.Y.
      • Johnson J.A.
      • Dover D.
      • Kaul P.
      Outcomes of singleton and twin pregnancies complicated by pre-existing diabetes and gestational diabetes: A population-based study in Alberta, Canada, 2005–11.
      ,
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,
      • Oster R.T.
      • King M.
      • Morrish D.W.
      • Mayan M.J.
      • Toth E.L.
      Diabetes in pregnancy among First Nations women in Alberta, Canada: a retrospective analysis.
      ,

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ,

      Australian women and their babies 2010 [Available from: https://www.adips.org/downloads/dip2010-aihw.pdf.

      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ,
      • Zhang X.
      • Xu H.
      • Hu R.
      • Xiong Y.u.
      • Gu W.
      • Zhou Q.
      • et al.
      Changing trends of adverse pregnancy outcomes with maternal age in primipara with singleton birth: A join point analysis of a multicenter historical cohort study in China in 2011–2012.
      ]; thirteen studies included pregnancies during 2011–2020 [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ,
      • Kalra B.
      • Kalra S.
      • Choudhary M.
      • Thakral M.
      Prevalence of Pharamcologically-treated Diabetes in Term Pregnancies in Haryana, India.
      ,
      • Deputy N.P.
      • Kim S.Y.
      • Conrey E.J.
      • Bullard K.M.
      Prevalence and Changes in Preexisting Diabetes and Gestational Diabetes Among Women Who Had a Live Birth - United States, 2012–2016.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • System N.O.I.
      ,
      • Soliman A.
      • Salama H.
      • Al Rifai H.
      • De Sanctis V.
      • Al-Obaidly S.
      • Al Qubasi M.
      • et al.
      The effect of different forms of dysglycemia during pregnancy on maternal and fetal outcomes in treated women and comparison with large cohort studies.
      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,
      • Adugna D.G.
      • Enyew E.F.
      • Jemberie M.T.
      Prevalence and Associated Factors of Macrosomia Among Newborns Delivered in University of Gondar Comprehensive Specialized Hospital, Gondar, Ethiopia: An Institution-Based Cross-Sectional Study.
      ,
      • Wahabi H.
      • Fayed A.
      • Esmaeil S.
      • Mamdouh H.
      • Kotb R.
      Prevalence and Complications of Pregestational and Gestational Diabetes in Saudi Women: Analysis from Riyadh Mother and Baby Cohort Study (RAHMA).
      ,
      • Gómez H.L.
      • Martínez M.L.
      • Rodríguez Z.M.
      Clinical and epidemiological profile of diabetes mellitus in pregnancy, Isle of Youth, 2008.
      ,
      • Eshetu B.
      • Sintayehu Y.
      • Mekonnen B.
      • Daba W.
      Birth Outcomes among Diabetic Mothers Who Delivered in Tikur Anbessa Specialized Hospital.
      ,
      • Sema V.
      • Naidu S.
      • Prevalence G.RJPJRH.
      ], nine during 1990–2010 [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ,
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ,
      • Xiang A.H.
      • Wang X.
      • Martinez M.P.
      • Walthall J.C.
      • Curry E.S.
      • Page K.
      • et al.
      Association of Maternal Diabetes With Autism in Offspring.
      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      , ], six during 2004–2015 [
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ,
      • Sormunen‐Harju H.
      • Koivusalo S.
      • Gissler M.
      • Metsälä J.
      ,

      The Drugs and Pregnancy project. Drugs and pregnancy 2018.

      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ], and one study had women who were pregnant during the period 1973–2012 [
      • Barrett P.M.
      • McCarthy F.P.
      • Evans M.
      • Kublickas M.
      • Perry I.J.
      • Stenvinkel P.
      • et al.
      Stillbirth is associated with increased risk of long-term maternal renal disease: a nationwide cohort study.
      ] [Supplementary Table 1].

      3.3 Risk of bias assessment of included data sources

      In the assessment of methodological quality, five data sources [
      • Deputy N.P.
      • Kim S.Y.
      • Conrey E.J.
      • Bullard K.M.
      Prevalence and Changes in Preexisting Diabetes and Gestational Diabetes Among Women Who Had a Live Birth - United States, 2012–2016.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • System N.O.I.
      ,

      The Drugs and Pregnancy project. Drugs and pregnancy 2018.

      ,
      • Sema V.
      • Naidu S.
      • Prevalence G.RJPJRH.
      ] were deemed to be of poor methodological quality. Of the remaining 37 contributions, 28 sources [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ,
      • Barrett P.M.
      • McCarthy F.P.
      • Evans M.
      • Kublickas M.
      • Perry I.J.
      • Stenvinkel P.
      • et al.
      Stillbirth is associated with increased risk of long-term maternal renal disease: a nationwide cohort study.
      ,
      • Kalra B.
      • Kalra S.
      • Choudhary M.
      • Thakral M.
      Prevalence of Pharamcologically-treated Diabetes in Term Pregnancies in Haryana, India.
      ,
      • Cynthia P.
      • Timothy S.
      • Isabelle E.
      What is the impact of diabetes for Australian Aboriginal women when pregnant?.
      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Fong A.
      • Serra A.
      • Herrero T.
      • Pan D.
      • Ogunyemi D.
      Pre-gestational versus gestational diabetes: a population based study on clinical and demographic differences.
      ,
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • Lai F.Y.
      • Johnson J.A.
      • Dover D.
      • Kaul P.
      Outcomes of singleton and twin pregnancies complicated by pre-existing diabetes and gestational diabetes: A population-based study in Alberta, Canada, 2005–11.
      ,
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,
      • Oster R.T.
      • King M.
      • Morrish D.W.
      • Mayan M.J.
      • Toth E.L.
      Diabetes in pregnancy among First Nations women in Alberta, Canada: a retrospective analysis.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ,
      • Soliman A.
      • Salama H.
      • Al Rifai H.
      • De Sanctis V.
      • Al-Obaidly S.
      • Al Qubasi M.
      • et al.
      The effect of different forms of dysglycemia during pregnancy on maternal and fetal outcomes in treated women and comparison with large cohort studies.
      ,
      • Sormunen‐Harju H.
      • Koivusalo S.
      • Gissler M.
      • Metsälä J.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,
      • Xiang A.H.
      • Wang X.
      • Martinez M.P.
      • Walthall J.C.
      • Curry E.S.
      • Page K.
      • et al.
      Association of Maternal Diabetes With Autism in Offspring.
      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ,

      Australian women and their babies 2010 [Available from: https://www.adips.org/downloads/dip2010-aihw.pdf.

      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      ,
      • Wahabi H.
      • Fayed A.
      • Esmaeil S.
      • Mamdouh H.
      • Kotb R.
      Prevalence and Complications of Pregestational and Gestational Diabetes in Saudi Women: Analysis from Riyadh Mother and Baby Cohort Study (RAHMA).
      ,
      • Gómez H.L.
      • Martínez M.L.
      • Rodríguez Z.M.
      Clinical and epidemiological profile of diabetes mellitus in pregnancy, Isle of Youth, 2008.
      ,
      • Eshetu B.
      • Sintayehu Y.
      • Mekonnen B.
      • Daba W.
      Birth Outcomes among Diabetic Mothers Who Delivered in Tikur Anbessa Specialized Hospital.
      ] were deemed to be of moderate quality and nine sources [
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ,
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,
      • Jaffe A.
      • Giveon S.
      • Rubin C.
      • Novikov I.
      • Ziv A.
      • Kalter-Leibovici O.
      Gestational diabetes risk in a multi-ethnic population.
      ,
      • Adugna D.G.
      • Enyew E.F.
      • Jemberie M.T.
      Prevalence and Associated Factors of Macrosomia Among Newborns Delivered in University of Gondar Comprehensive Specialized Hospital, Gondar, Ethiopia: An Institution-Based Cross-Sectional Study.
      ,

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      , ] of high methodological quality [Supplementary Table 2].

      3.4 Prevalence of pre-existing diabetes in pregnancy

      The raw prevalence of pre-existing diabetes in pregnancy ranged from 0.07% in China in one study during the period 2011–2012 [
      • Wahabi H.
      • Fayed A.
      • Esmaeil S.
      • Mamdouh H.
      • Kotb R.
      Prevalence and Complications of Pregestational and Gestational Diabetes in Saudi Women: Analysis from Riyadh Mother and Baby Cohort Study (RAHMA).
      ] to a high of 3.6% in a study [

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ] from Saudi Arabia with pregnancies during the period 2007–2009. The pooled prevalence of pre-existing diabetes varied across countries, from 0.5% [95 %CI 0.5–0.5] in Sweden to a high of 2.6% [95 %CI 2.2–2.8] in Saudi Arabia [Fig. 3 & Supplementary Table 3]. The overall pooled prevalence of pre-existing diabetes from all the 41 studies was 0.6% [95 %CI 0.3–1.0] with high between-study heterogeneity [I2 = 99.9%, p < 0.01] and evidence of publication bias [Supplementary Fig.1, Fig. 2].
      Figure thumbnail gr2
      Fig. 2Pooled prevalence of pre-existing diabetes in pregnancy per country. The marks are labelled by the pooled prevalence in each country.
      Figure thumbnail gr3
      Fig. 3– Prevalence of pre-existing diabetes by IDF region. *Abbreviations: pDM – pre-existing diabetes, NSW 2019 - Centre for Epidemiology and Evidence. New South Wales Mothers and Babies 2019, AIHW 2010 - Australian Institute of Health and Welfare 2010, NWH 2018 - National Women's Health 2018, NOIS 2018 - National Obstetrics Information System 2015–2019, DPS 2018 - Drugs and Pregnancy study 2018.

      3.5 Prevalence of pre-existing diabetes in pregnancy by IDF region

      The pooled prevalence varied across regions, with the lowest prevalence in Europe [0.5%, 95 %CI 0.4–0.7, I2 = 99.8%, p < 0.01] and the highest prevalence in the Middle East and North Africa [2.4%, 95 %CI 1.8–3.1, I2 = 91.5%, p < 0.01] [Fig. 3]. The pooled prevalence was similar, between 0.5% − 0.6% for the IDF regions of Australasia, Asia, Europe, and North America. In North America, the prevalence ranged from 0.5% in three studies from the USA and Canada [

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ] to 3.2% in one small study from the USA [
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ]. All the five studies from the Middle East and North Africa region had prevalence above 1%, with the highest prevalence of 3.5% and 3.6% reported from the two studies from Saudi Arabia[

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ]. In Europe, the lowest prevalence of 0.4% was from four studies from Spain and the UK [
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ]. Four studies from Sweden, Malta, Spain and the UK had prevalence between 0.5% and 0.6%[
      • Barrett P.M.
      • McCarthy F.P.
      • Evans M.
      • Kublickas M.
      • Perry I.J.
      • Stenvinkel P.
      • et al.
      Stillbirth is associated with increased risk of long-term maternal renal disease: a nationwide cohort study.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ], and the highest prevalence of 1.2% was from two studies from Finland[
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • Sormunen‐Harju H.
      • Koivusalo S.
      • Gissler M.
      • Metsälä J.
      ]. In Australasia, the lowest prevalence was 0.5% from Fiji during 2013–2015 [
      • Eshetu B.
      • Sintayehu Y.
      • Mekonnen B.
      • Daba W.
      Birth Outcomes among Diabetic Mothers Who Delivered in Tikur Anbessa Specialized Hospital.
      ], two studies from Australia reported prevalence between 0.5% and 0.6% [
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ,

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ] and the highest prevalence was 1.5% from one study [

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ] from New Zealand. Of the three studies from Asia, the lowest prevalence of 0.07% was from a cohort study [
      • Wahabi H.
      • Fayed A.
      • Esmaeil S.
      • Mamdouh H.
      • Kotb R.
      Prevalence and Complications of Pregestational and Gestational Diabetes in Saudi Women: Analysis from Riyadh Mother and Baby Cohort Study (RAHMA).
      ] from China while the highest prevalence of 1.2% was from a population-based cohort of 6.4 million women [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ] also from China. In Africa, only two studies, both from Ethiopia were available for inclusion, with a prevalence of 0.4% [
      • Adugna D.G.
      • Enyew E.F.
      • Jemberie M.T.
      Prevalence and Associated Factors of Macrosomia Among Newborns Delivered in University of Gondar Comprehensive Specialized Hospital, Gondar, Ethiopia: An Institution-Based Cross-Sectional Study.
      ] in one study and 1.4% in the other study [
      • Gómez H.L.
      • Martínez M.L.
      • Rodríguez Z.M.
      Clinical and epidemiological profile of diabetes mellitus in pregnancy, Isle of Youth, 2008.
      ].

      3.6 Prevalence of pre-existing diabetes in pregnancy by period of study

      Overall, there was a general trend towards increasing prevalence of pre-existing diabetes with time, from 0.5% [95 %CI 0.1–1.0] during the period 1990–2010 to 1.0% [95 %CI 0.6–1.5] during the period 2011–2020 [Supplementary Fig. 3]. When data from countries with repeated surveys across the time periods only were considered, the prevalence increased from 0.5% [95 %CI 0.1 – 1.1] during the period 1990 – 2010 to 0.8% [95 %CI 0.4 – 1.4] during 2011–2020 [Fig. 4]. This trend remained after the exclusion of the studies from Saudi Arabia, which had high prevalence compared to studies from the other countries with repeated surveys [Supplementary Fig. 4].
      Figure thumbnail gr4
      Fig 4- Prevalence of pre-existing diabetes in pregnancy by period of study for countries with repeated survey across the time periods only, *Abbreviations: pDM – pre-existing diabetes, NSW 2019 - Centre for Epidemiology and Evidence. New South Wales Mothers and Babies 2019, AIHW 2010 - Australian Institute of Health and Welfare 2010, NWH 2018 - National Women's Health 2018, NOIS 2018 - National Obstetrics Information System 2015–2019, DPS 2018 - Drugs and Pregnancy study 2018.

      3.7 Prevalence of pre-existing diabetes in pregnancy by age group

      Six studies, two each from Saudi Arabia and the USA[
      • Deputy N.P.
      • Kim S.Y.
      • Conrey E.J.
      • Bullard K.M.
      Prevalence and Changes in Preexisting Diabetes and Gestational Diabetes Among Women Who Had a Live Birth - United States, 2012–2016.
      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      ], and one each from Canada [
      • Schummers L.
      • Hutcheon J.A.
      • Hacker M.R.
      • VanderWeele T.J.
      • Williams P.L.
      • McElrath T.F.
      • et al.
      Absolute risks of obstetric outcomes by maternal age at first birth: a population-based cohort.
      ] and Finland [

      The Drugs and Pregnancy project. Drugs and pregnancy 2018.

      ], reported data on the prevalence of pre-existing diabetes by age group, with a total of 3 112 576 women. Although there was wide heterogeneity between the studies, there was a clear and sharp increase in the prevalence of pre-existing diabetes by age group; from the 20–29 years age group [0.5%, 95 %CI 0.2 – 1.0], 30–39 years [1.0%, 95 %CI 0.7 – 1.4] to the 40–49 years age group [1.8%, 95 %CI 1.0 – 2.8] [Supplementary Fig. 5]. Within the individual included studies, the prevalence also increased with the older age groups [Supplementary Fig. 5].
      Figure thumbnail gr5
      Fig. 5Prevalence of pre-existing T1D and T2D in pregnancy, *Abbreviations: pDM – pre-existing diabetes, NSW 2019 - Centre for Epidemiology and Evidence. New South Wales Mothers and Babies 2019, AIHW 2010 - Australian Institute of Health and Welfare 2010, NWH 2018 - National Women's Health 2018, NOIS 2018 - National Obstetrics Information System 2015–2019, DPS 2018 - Drugs and Pregnancy study 2018.

      3.8 Prevalence of pre-existing T1D in pregnancy

      Fifteen studies with 51 883 927 women, reported data on the prevalence of pre-existing T1D in pregnancy. Four of these studies were from the USA[

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,

      Australian women and their babies 2010 [Available from: https://www.adips.org/downloads/dip2010-aihw.pdf.

      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      ], three from the UK[
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ], three from Saudi Arabia [

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ], two from Spain[
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ], and one each from Sweden [
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ], New Zealand [

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ] and Australia [

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ]. The prevalence of pre-existing T1D in these studies was between 0.1% and 0.5%, except for the three studies from Saudi Arabia [

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ] [Fig. 5]. The pooled prevalence of pre-existing T1D was 0.3% [95 %CI 0.2–0.4], with high heterogeneity between studies [I2 = 99.6%, p < 0.01] and evidence of publication bias [Supplementary Fig. 5]. The pooled prevalence was similar across the IDF regions of Australasia [0.3%], North America [0.3%] and Europe [0.3%] but higher in the Middle East and North Africa region [0.9%] [Fig. 5]. There were not enough studies to analyse trends with time.

      3.9 Prevalence of pre-existing T2D in pregnancy

      Nineteen studies[

      Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK, Kourtis AP, et al. Diabetes trends among delivery hospitalizations in the U.S., 1994-2004. Diabetes care. 2010;33(4):768-73.

      ,
      • Kalra B.
      • Kalra S.
      • Choudhary M.
      • Thakral M.
      Prevalence of Pharamcologically-treated Diabetes in Term Pregnancies in Haryana, India.
      ,

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ,
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ,
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ,
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Martinez M.P.
      • Lin J.
      • Chow T.
      • Chung J.
      • Wang X.
      • Xiang A.H.
      Maternal Gestational Diabetes and Type 2 Diabetes During Pregnancy and Risk of Childhood Asthma in Offspring.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,
      • Xiang A.H.
      • Wang X.
      • Martinez M.P.
      • Walthall J.C.
      • Curry E.S.
      • Page K.
      • et al.
      Association of Maternal Diabetes With Autism in Offspring.
      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ,

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ,

      Australian women and their babies 2010 [Available from: https://www.adips.org/downloads/dip2010-aihw.pdf.

      ,
      • Jovanovič L.
      • Liang Y.
      • Weng W.
      • Hamilton M.
      • Chen L.
      • Wintfeld N.
      Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy.
      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ], with 52 892 280 women, provided data on the prevalence of pre-existing type 2 diabetes. Five of the studies were from the USA, three from the UK[
      • Coton S.J.
      • Nazareth I.
      • Petersen I.
      A cohort study of trends in the prevalence of pregestational diabetes in pregnancy recorded in UK general practice between 1995 and 2012.
      ,
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ], three from Saudi Arabia [

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ,
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ,

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ], two from Spain[
      • López-de-Andrés A.
      • Perez-Farinos N.
      • Hernández-Barrera V.
      • Palomar-Gallego M.A.
      • Carabantes-Alarcón D.
      • Zamorano-León J.J.
      • et al.
      A Population-Based Study of Diabetes during Pregnancy in Spain (2009–2015): Trends in Incidence, Obstetric Interventions, and Pregnancy Outcomes.
      ,
      • Gortazar L.
      • Goday A.
      • Flores-Le Roux J.A.
      • Sarsanedas E.
      • Payà A.
      • Mañé L.
      • et al.
      Trends in prevalence of pre-existing diabetes and perinatal outcomes: a large, population-based study in Catalonia, Spain, 2006–2015.
      ], and one each from Sweden [
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ], Canada [
      • Davenport M.H.
      • Campbell M.K.
      • Mottola M.F.
      Increased incidence of glucose disorders during pregnancy is not explained by pre-pregnancy obesity in London.
      ], Finland [
      • Kong L.
      • Nilsson I.A.K.
      • Gissler M.
      • Lavebratt C.
      Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity.
      ], New Zealand [

      National Women’s Health ADHB. Annual Clinical Report 2018 [Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/ACR/NWH-Annual-Clinical-Report-2018-final.pdf.

      ] and Australia [

      Australian Institute of Health and Welfare. Diabetes in pregnancy: its impact on

      ]. The prevalence of pre-existing T2D ranged from 0.1% in Sweden [
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ] to 2.9% in Saudi Arabia [

      Al-Rubeaan K, Al-Manaa HA, Khoja TA, Youssef AM, Al-Sharqawi AH, Siddiqui K, et al. A community-based survey for different abnormal glucose metabolism among pregnant women in a random household study (SAUDI-DM). BMJ open. 2014;4(8):e005906.

      ] [Fig. 5]. The pooled prevalence of pre-existing T2D was 0.2% [95 %CI 0.0–0.9] [Fig. 5], with high heterogeneity between the studies [I2 = 100%, p < 0.01], and evidence of publication bias [Supplementary Fig. 6]. The prevalence also varied by IDF region with the lowest in North America [0.2%] and the highest in the Middle East and North Africa region [1.5%] [Fig. 5].

      4. Discussion

      In this systematic review and meta-analysis of 42 studies from 17 countries, we found that the prevalence of pre-existing diabetes in pregnancy was 0.6% and: 1] varied globally, with the highest prevalence of 2.4% in the Middle East and North Africa and the lowest, 0.5%, in the Europe IDF regions; 2] increased with age group, from 0.5% in women aged 20–29 years, 1.0% in those aged 30–39 years, to 1.8% in women aged 40–49 years; 3] doubled from 0.5% in 1990–2010 to 1.0% in 2011–2020; 4] was 0.3% and 0.2% in T1D and T2D respectively; and was highest for both types in the Middle East and North Africa compared to other IDF regions.
      Apart from one meta-analysis which compared the prevalence of pre-existing diabetes in pregnancy between indigenous and non-indigenous populations [
      • Correa A.
      • Bardenheier B.
      • Elixhauser A.
      • Geiss L.S.
      • Gregg E.
      Trends in prevalence of diabetes among delivery hospitalizations, United States, 1993–2009.
      ], to our knowledge, this is the first systematic review and meta-analysis of the global prevalence of pre-existing diabetes. Thus, we are unable to carry out comparisons with existing reviews. As expected, the prevalence of pre-existing diabetes was higher in older age groups and higher in the regions with a higher prevalence of T2D, in this case, the Middle East and North Africa region. However, the lack of data from other regions means that a lot of uncertainty in the estimates remains. Apart from the lack of data from many countries, our findings may have underestimated the true prevalence of pre-existing diabetes in pregnancy. Most of the included studies used existing T1D and T2D diagnoses in estimating the prevalence of pre-existing diabetes. Consequently, women with undiagnosed diabetes would have been missed. Missing this group is particularly pertinent in the LMICs where the proportion of diagnosed diabetes tends to be low [

      International Diabetes Federation. IDF Diabetes Atlas 9th Edition: International Diabetes Federation.; 2019 [cited 2020 13 January]. 9:[Available from: http://www.diabetesatlas.org.

      ]. In China, for example, most women with pre-existing diabetes in pregnancy were not previously diagnosed; only 917 out of 76 297 [1.2%] of women who had diabetes and later became pregnant were aware of their diabetes status [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ]. Apart from this study from China [

      Wei Y, Xu Q, Yang H, Yang Y, Wang L, Chen H, et al. Preconception diabetes mellitus and adverse pregnancy outcomes in over 6.4 million women: A population-based cohort study in China. PLoS medicine. 2019;16(10):e1002926.

      ], no other study assessed diabetes status prior to conception. The denominators used to estimate pre-existing diabetes in our included studies also contribute to underestimation of the prevalence of pre-existing diabetes in pregnancy, as most of the studies used either total births or live births as denominators, while only a few used total pregnancies. Measuring the prevalence of pre-existing diabetes from births is likely to result in underestimation of true prevalence as this leaves out women with pregnancy loss, to which women with diabetes in pregnancy are more susceptible [
      • Wahabi H.A.
      • Esmaeil S.A.
      • Fayed A.
      • Al-Shaikh G.
      • Alzeidan R.A.
      Pre-existing diabetes mellitus and adverse pregnancy outcomes.
      ]. Good-quality studies, preferably prospective in design, beginning during the preconception period, are needed, especially in the IDF regions of sub-Saharan Africa, Asia, and South America.
      Our findings suggest that the prevalence of pre-existing diabetes in pregnant women has doubled during the period 1990–2020. This increase in prevalence is mainly based on the findings from large studies from the UK [
      • Murphy H.R.
      • Bell R.
      • Cartwright C.
      • Curnow P.
      • Maresh M.
      • Morgan M.
      • et al.
      Improved pregnancy outcomes in women with type 1 and type 2 diabetes but substantial clinic-to-clinic variations: a prospective nationwide study.
      ,
      • Patel S.
      • Fraser A.
      • Davey Smith G.
      • Lindsay R.S.
      • Sattar N.
      • Nelson S.M.
      • et al.
      Associations of Gestational Diabetes, Existing Diabetes, and Glycosuria With Offspring Obesity and Cardiometabolic Outcomes.
      ,
      • Tennant P.W.G.
      • Glinianaia S.V.
      • Bilous R.W.
      • Rankin J.
      • Bell R.
      Pre-existing diabetes, maternal glycated haemoglobin, and the risks of fetal and infant death: a population-based study.
      ], Canada [
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ], the USA [
      • Voaklander B.
      • Rowe S.
      • Sanni O.
      • Campbell S.
      • Eurich D.
      • Ospina M.B.
      Prevalence of diabetes in pregnancy among Indigenous women in Australia, Canada, New Zealand, and the USA: a systematic review and meta-analysis.
      ], Australia [
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ], the Saudi Arabia [

      Peng TY, Ehrlich SF, Crites Y, Kitzmiller JL, Kuzniewicz MW, Hedderson MM, et al. Trends and racial and ethnic disparities in the prevalence of pregestational type 1 and type 2 diabetes in Northern California: 1996-2014. Am J Obstet Gynecol. 2017;216(2):177.e1-.e8.

      ], and Sweden [
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ]. In these countries, there were large increases in the prevalence of pre-existing diabetes in pregnancy over relatively short periods of time. For example, in Canada, the prevalence of pre-existing diabetes doubled from 0.7% to 1.5% between 1996 and 2010 in one study [
      • Feig D.S.
      • Hwee J.
      • Shah B.R.
      • Booth G.L.
      • Bierman A.S.
      • Lipscombe L.L.
      Trends in incidence of diabetes in pregnancy and serious perinatal outcomes: a large, population-based study in Ontario, Canada, 1996–2010.
      ], in Australia [
      • Abouzeid M.
      • Versace V.L.
      • Janus E.D.
      • Davey M.-A.
      • Philpot B.
      • Oats J.
      • et al.
      A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008.
      ], the prevalence increased from 0.4% to 0.6% during 1999–2008, and in Sweden [
      • Fadl H.E.
      • Simmons D.
      Trends in diabetes in pregnancy in Sweden 1998–2012.
      ], the prevalence of T1D and T2D increased by 33% and 111%, respectively. The prevalence of pre-existing diabetes in pregnancy is likely increasing in other regions and countries where we did not have data, especially in the low and middle-income countries, driven by the concomitant increases in the population prevalence of obesity and T2D during the last 40 years [
      • Kitzmiller J.L.
      • Ferrara A.
      • Peng T.
      • Cissell M.A.
      • Kim
      ,
      NCD Risk Factor Collaboration
      Worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4· 4 million participants.
      ]. Other factors that may contribute to the rising prevalence of pre-existing diabetes in pregnancy include the higher prevalence of women getting pregnant at advanced ages [
      • Kenny L.C.
      • Lavender T.
      • McNamee R.
      • O’Neill S.M.
      • Mills T.
      • Khashan A.S.
      • et al.
      Advanced maternal age and adverse pregnancy outcome: evidence from a large contemporary cohort.
      ] and the increase in the prevalence of T2D in the young [
      • Likitmaskul S.
      • Kiattisathavee P.
      • Chaichanwatanakul K.
      • Punnakanta L.
      • Angsusingha K.
      • Tuchinda C.
      Increasing prevalence of type 2 diabetes mellitus in Thai children and adolescents associated with increasing prevalence of obesity.
      ,
      • Kao K.T.
      • Sabin M.A.
      Type 2 diabetes mellitus in children and adolescents.
      ,
      • Pulgaron E.R.
      • Delamater A.M.
      Obesity and type 2 diabetes in children: epidemiology and treatment.
      ]. In Africa, there is some evidence that the burden of T2D in women of childbearing age is considerable, with an estimated prevalence of 7% from a recent review [
      • Chivese T.
      • Werfalli M.M.
      • Magodoro I.
      • Chinhoyi R.L.
      • Kengne A.P.
      • Norris S.A.
      • et al.
      Prevalence of type 2 diabetes mellitus in women of childbearing age in Africa during 2000–2016: a systematic review and meta-analysis.
      ]. There are several implications of the rising prevalence of pre-existing diabetes in pregnancy. Countries need to prepare for additional resource allocation for diabetes care during preconception, pregnancy, and the postnatal period. There is also a need to increase awareness of the adverse effects of diabetes in pregnancy in women intending to become pregnant.
      As expected, most of the prevalent pre-existing diabetes in pregnancy was due to T1D, with a prevalence of 0.3% compared to a prevalence of 0.2% for T2D. This is mostly due to the relatively young age (30 years) at conception for most of the women in the included studies. However, less than half of the studies reported data on T1D and T2D separately, again emphasising the need for more research in this area.
      Apart from the limitations in the included studies that we have already discussed, such as the use of live births as denominators, there was an under-representation of studies in regions other than North America and Western Europe. We could not identify studies from South America, we identified only two studies from Africa, both from Ethiopia, and three from Asia, of which two were from China. The unexplained high heterogeneity in our analyses limits the application of our estimates to the many countries without data. We were not able to adequately analyse the trends in the prevalence of pre-existing diabetes in pregnancy because many of the included studies had pregnancies from time periods that were not mutually exclusive. A strength of this study is that we comprehensively searched for all eligible studies and rigorously carried out the study following the PRISMA guidelines.

      5. Conclusion

      The prevalence of pre-existing diabetes in pregnancy ranges from 0.5% to 2.4%- while this is low, it appears to have doubled during the period 1990–2020. High-quality studies are needed to estimate the prevalence of pre-existing diabetes in pregnancy, especially in the LMICs.

      Funding

      No funding to report.

      CRediT authorship contribution statement

      Tawanda Chivese: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization, Writing – original draft, Writing – review & editing. Cecilia A. Hoegfeldt: Data curation, Investigation, Visualization, Writing – original draft, Writing – review & editing. Mahmoud Werfalli: Investigation, Methodology, Formal analysis, Writing – review & editing. Lili Yuen: Investigation, Writing – review & editing. Hong Sun: Investigation, Writing – review & editing. Suvi Karuranga: Investigation, Writing – review & editing. Ninghua Li: Investigation, Writing – review & editing. Akhil Gupta: Investigation, Writing – review & editing. Jincy Immanuel: Investigation, Writing – review & editing. Hema Divakar: Investigation, Writing – review & editing. Camille E. Powe: Investigation, Writing – review & editing. Naomi S Levitt: Formal analysis, Investigation, Methodology, Supervision, Validation, Visualization, Writing – review & editing. Xilin Yang: Conceptualization, Formal analysis, Methodology, Validation, Writing – review & editing. David Simmons: Conceptualization, Formal analysis, Investigation, Methodology, Supervision, Validation, Visualization, Writing – review & editing.

      Declaration of Competing Interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Acknowledgements

      The authors are grateful to the authors of the included original studies for provision of additional data.

      Appendix A. Supplementary data

      The following are the Supplementary data to this article:

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