Abstract
OBJECTIVE: Increasing numbers of pregnancies are complicated by pregestational diabetes mellitus, especially type 2 diabetes (T2DM). Some studies have reported similar or greater risks of adverse pregnancy outcomes among women with T2DM relative to type 1 diabetes (T1DM). We aimed to compare the risk of four pregnancy complications: pre-eclampsia, preterm delivery, macrosomia, and perinatal mortality, in pregnant women with T2DM vs T1DM in high-income countries. DESIGN: Systematic review with meta-analyses. METHODS: Systematic literature searches in Medline and Embase were performed. We included observational studies with original data of outcome occurrence in both women with pregestational T2DM and T1DM. Two researchers independently evaluated full-text studies for inclusion and assessed the risk of bias using the Newcastle-Ottawa scale. Finally, we performed four meta-analyses. RESULTS: We included 35 publications in total. Meta-analyses demonstrated that, compared to T1DM, T2DM was associated with a lower risk of pre-eclampsia (risk ratio (RR): 0.76; 95% CI: 0.68-0.85), preterm delivery (RR: 0.69; 95% CI: 0.62-0.77), and macrosomia (RR: 0.75; 95% CI: 0.60-0.94). Perinatal mortality was more likely in pregnancies with T2DM (RR: 1.26; 95% CI: 1.06-1.50). CONCLUSION: A summation of the research literature demonstrated that, compared to T1DM, women with T2DM had a lower risk of pre-eclampsia, preterm delivery, and macrosomia, but a higher risk of perinatal mortality. SIGNIFICANCE STATEMENT: Our review of pregnant women with diabetes suggests a higher risk of perinatal mortality for cases with maternal type 2 diabetes, even though the risks of pre-eclampsia, preterm delivery, and macrosomia were higher in cases with type 1 diabetes. Hence, the prevention of the development of type 2 diabetes and focus on improved gestational and diabetic care could be beneficial for fetal health.