Context:Multiple consensus statements decree that women with diabetes mellitus should have comparable birth outcomes to women without diabetes mellitus; however, there is a scarcity of contemporary population-based studies on this issue.Objective:To examine temporal trends in obstetric interventions and perinatal outcomes in a population-based cohort of women with type 1, type 2, or gestational diabetes mellitus compared with a control population.Design:Cross-sectional study.Setting:National hospitalization data (Canada except Quebec) from 2004 to 2015.Patients:Pregnant women with type 1 (n = 7362), type 2 (n = 11,028), and gestational diabetes mellitus (n = 149,780) and women without diabetes mellitus (n = 2,688,231).Main Outcome Measures:Rates of obstetric intervention, maternal morbidity, and neonatal morbidity/mortality.Results:A consistent relationship was generally observed between diabetes mellitus subtype and obstetric outcomes, with women with type 1 diabetes mellitus having the highest rate of intervention and the highest rates of adverse perinatal outcomes followed by women with type 2 diabetes mellitus and women with gestational diabetes mellitus. Rates of severe preeclampsia were 1.2% among women without diabetes mellitus, 2.1% among women with gestational diabetes mellitus, 4.2% among women with type 2 diabetes mellitus, and 7.5% among women with type 1 diabetes mellitus (P < 0.001). The rate of neonatal morbidity ranged from 8.7% in women without diabetes mellitus to 11.0%, 17.4%, and 24.1% in women with gestational, type 2, and type 1 diabetes mellitus, respectively (P < 0.001).Conclusions:In a contemporary obstetric population, women with diabetes mellitus remain at increased risk of adverse pregnancy outcomes compared with women without diabetes mellitus.

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Introduction Women with diabetes, and their infants, have an increased risk of adverse events due to excess fetal growth. Earlier delivery, when fetuses are smaller, may reduce these risks. This study aimed to evaluate the week‐specific risks of maternal and neonatal morbidity/mortality to assist with obstetrical decision making. Material and methods In this population‐based cohort study, women with type 1 diabetes (n = 5889), type 2 diabetes (n = 9422) and gestational diabetes (n = 138 917) and a comparison group without diabetes (n = 2 553 243) who delivered a singleton infant at ≥36 completed weeks of gestation between 2004 and 2014 were identified from the Canadian Institute of Health Information Discharge Abstract Database. Multivariate logistic regression was used to determine the week‐specific rates of severe maternal and neonatal morbidity/mortality among women delivered iatrogenically vs those undergoing expectant management. Results For all women, the absolute risk of severe maternal morbidity/mortality was low, typically impacting less than 1% of women, and there was no significant difference in gestational age‐specific severe maternal morbidity/mortality between iatrogenic delivery and expectant management among women with any form of diabetes. Among women with gestational diabetes, iatrogenic delivery was associated with an increased risk of neonatal morbidity/mortality compared with expectant management at 36 and 37 weeks’ gestation (76.7 and 27.8 excess cases per 1000 deliveries, respectively) and a lower risk of neonatal morbidity/mortality at 38, 39 and 40 weeks’ gestation (7.9, 27.3 and 15.9 fewer cases per 1000 deliveries, respectively). Increased risks of severe neonatal morbidity following iatrogenic delivery compared with expectant management were also observed for women with type 1 diabetes at 36 (98.3 excess cases per 1000 deliveries) and 37 weeks’ gestation (44.5 excess cases per 1000 deliveries) and for women with type 2 diabetes at 36 weeks’ gestation (77.9 excess cases per 1000 deliveries) weeks. Conclusions The clinical decision regarding timing of delivery is complex and contingent on maternal‐fetal wellbeing, including adequate glycemic control. This study suggests that delivery at 38, 39 or 40 weeks’ gestation may optimize neonatal outcomes among women with diabetes.