Greater risk of type 2 diabetes progression in multifetal gestations with gestational diabetes: the impact of obesity

Background: The relationship between gestational diabetes mellitus and adverse outcomes in multifetal pregnancies is complex and controversial. Moreover, limited research has focused on the risk of gestational diabetes mellitus progression to type 2 diabetes mellitus specifically in multifetal pregnancies, resulting in conflicting results from existing studies. Objective: This study aimed to assess the risk of gestational diabetes mellitus progression to type 2 diabetes mellitus between singleton and multifetal pregnancies in a large cohort of parturients with a 5-year follow-up. Study Design: A retrospective study was conducted on a prospective cohort of pregnant individuals with pregnancies between January 1, 2017, and December 31, 2020, followed up to 5 years after delivery. Glucose levels during pregnancy were obtained from the Meuhedet Health Maintenance Organization laboratory system and cross-linked with the Israeli National Diabetes Registry. The cohort was divided into 4 groups: singleton pregnancy without gestational diabetes mellitus, singleton pregnancy with gestational diabetes mellitus, multifetal pregnancy without gestational diabetes mellitus, and multifetal pregnancy with gestational diabetes mellitus. Gestational diabetes mellitus was defined according to the American Diabetes Association criteria using the 2-step strategy. Univariate analyses, followed by survival analysis that included Kaplan-Meier hazard curves and Cox proportional-hazards models, were used to assess differences between groups and calculate the adjusted hazard ratios with 95% confidence intervals for progression to type 2 diabetes mellitus. Results: Among 88,611 parturients, 61,891 cases met the inclusion criteria. The prevalence of type 2 diabetes mellitus was 6.5% in the singleton pregnancy with gestational diabetes mellitus group and 9.4% in the multifetal pregnancy with gestational diabetes mellitus group. Parturients with gestational diabetes mellitus, regardless of plurality, were older and had higher fasting plasma glucose levels in the first trimester of pregnancy. The rates of increased body mass index, hypertension, and earlier gestational age at delivery were significantly higher in the gestational diabetes mellitus group among patients with singleton pregnancies but not among patients with multifetal pregnancies. Survival analysis demonstrated that gestational diabetes mellitus was associated with adjusted hazard ratios of type 2 diabetes mellitus of 4.62 (95% confidence interval, 3.69–5.78) in singleton pregnancies and 9.26 (95% confidence interval, 2.67–32.01) in multifetal pregnancies (P<.001 for both). Stratified analysis based on obesity status revealed that, in parturients without obesity, gestational diabetes mellitus in singleton pregnancies increased the risk of type 2 diabetes mellitus by 10.24 (95% confidence interval, 6.79–15.44; P<.001) compared with a nonsignificant risk in multifetal pregnancies (adjusted hazard ratio, 9.15; 95% confidence interval, 0.92–90.22; P=.059). Among parturients with obesity, gestational diabetes mellitus was associated with an increased risk of type 2 diabetes mellitus for both singleton and multifetal pregnancies (adjusted hazard ratio, 3.66; [95% confidence interval, 2.81–4.67; P<.001] and 9.31 [95% confidence interval, 2.12–40.76; P=.003], respectively). Conclusion: Compared with gestational diabetes mellitus in singleton pregnancies, gestational diabetes mellitus in multifetal pregnancies doubles the risk of progression to type 2 diabetes mellitus. This effect is primarily observed in patients with obesity. Our findings underscore the importance of providing special attention and postpartum follow-up for patients with multifetal pregnancies and gestational diabetes mellitus, especially those with obesity, to enable early diagnosis and intervention for type 2 diabetes mellitus.