To the Editor The increasing prevalence of gestational diabetes (GDM) and the surge in glyburide use for the treatment of GDM highlight the need for continued research within this area, and we therefore read the article by Camelo Castillo et al1 titled “Association of Adverse Pregnancy Outcomes With Glyburide vs Insulin in Women with Gestational Diabetes” and the accompanying editorial2 with great interest. The results of this study are thought provoking, but we are concerned that the limitations of their study design preclude attribution of the increased risk for neonatal intensive care unit admission, respiratory distress syndrome, and large for gestational age to glyburide use. While glyburide remains one possible cause of increased neonatal risks, both maternal obesity and gestational age at delivery are important potential confounding variables. Although the authors provide one reference for the sensitivity of International Classification of Diseases, Ninth Revision codes for obesity in pregnancy, others have found even lower sensitivities for the diagnosis of obesity3 and we are concerned that obesity may not have been adequately accounted for in their analyses. In addition, even among term gestations the risk for neonatal morbidity varies greatly by gestational age, so the lack of information regarding gestational age at delivery is significant.
Feghali MN, Scifres CM, Caritis SN. Glyburide vs Insulin and Adverse Pregnancy Outcomes. JAMA Pediatr. 2015;169(10):974. doi:10.1001/jamapediatrics.2015.1805