Adverse outcomes are more likely to occur in babies born to mothers with gestational diabetes compared with those born to non-diabetic mothers.
A study in Diabetologia examined the 796,346 deliveries that took place in France after 22 weeks of gestation in 2012, using data from hospital discharges and the national health insurance system.
"Complications of gestational diabetes are well known, such as preterm birth, macrosomia, preeclampsia, and Caesarean section, for example, but large-scale study is rare," one of the co-authors, Sophie Jacqueminet, MD, of Assistance Publique Hôpitaux de Paris, the city's public hospital system, told MedPage Today. "Our study, by limiting the analyses after 28 weeks of gestation, avoided immortal time bias and highlighted the real level of risk of gestational diabetes ... Furthermore, we observed a higher risk of respiratory distress, which had not been clearly established before."
Of the original cohort, 57,629 mothers (7.24%) had gestational diabetes. Investigators then further filtered the analysis to include only deliveries after 28 weeks, the point at which gestational diabetes usually begins to appear, and 37 weeks, to determine the risk of adverse outcomes in term deliveries.
Mothers with gestational diabetes were identified based on their use of glucose-lowering agents, hospital diagnosis at delivery, and overall medical history. Gestational diabetes was classified as "insulin-treated" when insulin was dispensed at least once during pregnancy. Further, as a way of filtering out mothers with undiagnosed pregestational diabetes, Jacqueminet and colleagues excluded those who received insulin or oral glucose-lowering agents at least once during the year after pregnancy.
After the analysis was limited to deliveries after 28 weeks to reduce immortal time bias, the risks of preterm birth (OR 1.3 [95% CI 1.3-1.4]), Caesarean section (OR 1.4 [95% CI 1.4-1.4]), pre-eclampsia/eclampsia (OR 1.7 [95% CI 1.6-1.7]), macrosomia (OR 1.8 [95% CI 1.7-1.8]), respiratory distress (OR 1.1 [95% CI 1.0-1.3]), birth trauma (OR 1.3 [95% CI 1.1-1.5]), and cardiac malformations (OR 1.3 [95% CI 1.1-1.4]) all increased in women with gestational diabetes compared with those without diabetes.
For deliveries after 37 weeks, the odds ratio initially rose by 30% for perinatal death in the gestational group compared with the non-diabetes group. No significant differences were observed for the other outcomes in deliveries after 28 weeks.
After this unexpected finding, the investigators then excluded women with gestational diabetes who received glucose-lowering agents at least once during the year after pregnancy. This analysis excluded 1,376 women in the group of deliveries after 28 weeks (6.8% in the insulin-treated group and 0.7% in the non-insulin-treated group) and 1,171 women in the group of deliveries after 37 weeks (7.3% in the insulin-treated group and 0.64% in the non-insulin-treated group).
In this more restricted group, the risk of respiratory distress among deliveries after 28 weeks and of perinatal death among deliveries after 37 weeks in the insulin-treated group were no longer significantly increased (OR 1.0 [95% CI 0.9-1.1] and OR 0.9 [95% CI 0.6-1.5], respectively), the team reported.
However, the risk of perinatal death among deliveries after 37 weeks remained moderately increased in the non-insulin-treated group (OR 1.3 [95% CI 1.0-1.6]).
"The risk of perinatal death is controversial during gestational diabetes in different studies," Jacqueminet noted. "Most of the time this risk is not increased, but after limiting the analysis after 37 weeks, the risk of perinatal death was slightly increased."
The findings underscore the importance of vigilance when treating those with gestational diabetes, she continued: "For physicians and other providers, it is important to consider gestational diabetes with caution even when women are not treated by insulin. Careful monitoring at the end of pregnancy should be implemented to decide the better time to give birth."
Jacqueminet said that moving forward, researchers "need to better know these women," including more about factors like age and body mass index, time of diagnosis, and glucose level at diagnosis.
The authors note that the study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
The researchers reported having no relationships with industry.
