Gestational diabetes mellitus (GDM) is the development of increased blood glucose levels during pregnancy as a result of increasing insulin resistance and pancreatic β-cell function being insufficient.1,2 The American Diabetes Association (ADA) classifies gestational diabetes as any degree of glucose intolerance that first develops during pregnancy in women who don’t already have a diabetes diagnosis,3 although some women diagnosed with gestational diabetes may not have true gestational diabetes but rather have previously undiagnosed diabetes.2,4 By definition, GDM is only present during gestation and is understood to go away after birth.
Although women often return to a euglycemic state postpartum, the literature overwhelmingly demonstrates that a history of GDM increases the risk of later developing type 2 diabetes (T2DM). Additionally, GDM and T2DM share a number of risk factors, including older age, obesity, past history of personal or familial diabetes, or abnormal glucose tolerance.3,5
In a 2008 population-based study in Ontario, Canada, 18.9% of women with GDM went on to develop T2DM within nine years post-partum. This is compared to 1.95% of women without GDM developing T2DM post-partum.2 The most significant risk factor for the development of T2DM was previous GDM.
A 2020 meta-analysis of 20 observational studies published from 2002-2019 assessed incidence of T2DM in women with GDM.6 Every study included showed a greater risk for T2DM in women with GDM, with a pooled T2DM incidence of 18.5% among women with GDM compared to 1.9% among controls.
A more recent study in the United Kingdom in 2018 (n=9,118) found that over a median follow-up of 2.9 years, women with GDM had a 9.82% chance of developing T2DM after pregnancy compared to 0.38% of women in the control group.7 The study also found that despite this risk, follow-up T2DM glycemic screening for women with GDM was inconsistent, with less than 60% screened in the year after delivery, and which reduced to 40% two years after delivery. The women with GDM in the study also exhibited higher risk for developing other health conditions, including hypertension (incidence 3.15% vs 1.31% control) and coronary heart disease (incidence 0.15% vs 0.06% control), further emphasizing the importance of consistent preventive care post-delivery.
The ADA recommends that women with GDM should be tested on their glycemic status at least 4-12 weeks after delivery and continue to have lifelong screening every 1-3 years depending on an individual’s risk factors.4 Recommended screening methods include hemoglobin A1c, fasting plasma glucose, and 2-hour plasma glucose during oral glucose tolerance test.5 The American College of Obstetricians and Gynecologists (ACOG) advises that screening during the delivery hospitalization in the immediate postpartum period is a reasonable alternative to testing at 4-12 weeks postpartum.8
The ADA further recommends postdelivery lifestyle interventions to further reduce risk of developing T2DM.4 A 2020 meta-analysis of 10 randomized control trials (n=1,733) examined the effect of lifestyle interventions on T2DM risk among women with GDM.9 Lifestyle interventions including increased physical activity, improved diet, or both were highly effective at reducing the risk of developing T2DM, with 6.14% of women in intervention groups developing T2DM compared to 10.69% of controls.
Breastfeeding may also offer some risk reduction for the development of T2DM. A 2020 prospective cohort study of women with a history of GDM (n=4,372) followed for 87,411 person-years of follow-up found that longer duration of breastfeeding was associated with lower risk of developing T2DM after adjusting for age, ethnicity, family history, parity, age at first birth, smoking status, diet, level of physical activity, and pre-pregnancy body mass index (BMI).10 The incidence of T2DM among those who didn’t breastfeed was 12.23 per 1,000 person-years. For those who breastfed for up to six months, the incidence was 12.14 per 1,000 person-years (Hazard Ratio [HR] 1.04); for >6-12 months of breastfeeding, incidence was 9.43 (HR 0.91); for >12-24 months of breastfeeding, incidence was 9.21 (HR 0.85); and for >24 months of breastfeeding, incidence was 8.43 (HR 0.73; p=0.003 for all).
A 2015 prospective cohort study of women with GDM (n=1,035) found that exclusively breastfeeding lowered the risk for developing T2DM within the two year follow-up period compared to exclusive formula feeding or mixed feeding methods.11 Among those who exclusively formula fed, the incidence rate of T2DM was 8.79 compared to 6.47 for those who mostly formula fed, 4.88 for those who mostly breastfed, and 3.95 for those who exclusively breastfed.
References
- Kleinwechter H, Schäfer-Graf U, Bührer C, et al. Gestational Diabetes Mellitus (GDM) Diagnosis, Therapy and Follow-Up Care. Experimental and Clinical Endocrinology & Diabetes. 2014;122(07):395-405.
- Feig DS, Zinman B, Wang X, Hux JE. Risk of development of diabetes mellitus after diagnosis of gestational diabetes. Canadian Medical Association Journal. 2008;179(3):229-234.
- American Diabetes A. Gestational Diabetes Mellitus. Diabetes Care. 2004;27(suppl_1):s88-s90.
- 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes-2024. Diabetes Care. 2024;47(Suppl 1):S282-s294.
- 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2024. Diabetes Care. 2024;47(Suppl 1):S20-s42.
- Vounzoulaki E, Khunti K, Abner SC, Tan BK, Davies MJ, Gillies CL. Progression to type 2 diabetes in women with a known history of gestational diabetes: systematic review and meta-analysis. BMJ (Clinical research ed). 2020:m1361.
- Daly B, Toulis KA, Thomas N, et al. Increased risk of ischemic heart disease, hypertension, and type 2 diabetes in women with previous gestational diabetes mellitus, a target group in general practice for preventive interventions: A population-based cohort study. PLOS Medicine. 2018;15(1):e1002488.
- ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum. Obstetrics & Gynecology. 2024;144(1):e20-23.
- Li N, Yang Y, Cui D, et al. Effects of lifestyle intervention on long-term risk of diabetes in women with prior gestational diabetes: A systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2021;22(1):e13122.
- Ley SH, Chavarro JE, Li M, et al. Lactation Duration and Long-term Risk for Incident Type 2 Diabetes in Women With a History of Gestational Diabetes Mellitus. Diabetes Care. 2020;43(4):793-798.
- Gunderson EP, Hurston SR, Ning X, et al. Lactation and Progression to Type 2 Diabetes Mellitus After Gestational Diabetes Mellitus: A Prospective Cohort Study. Annals of internal medicine. 2015;163(12):889-898.
