Timing of treatment initiation for mild gestational diabetes mellitus and perinatal outcomes

OBJECTIVE: The purpose of this study was to examine the association between gestational age (GA) at the time of treatment initiation for gestational diabetes mellitus (GDM) and maternal and perinatal outcomes. STUDY DESIGN: We conducted a secondary analysis of a multicenter randomized treatment trial of mild GDM in which women with mild GDM were assigned randomly to treatment vs usual care. The primary outcome of the original trial, as well as this analysis, was a composite perinatal adverse outcome that included neonatal hypoglycemia, hyperbilirubinemia, hyperinsulinemia, and perinatal death. Other outcomes that were examined included the frequency of large for GA, birthweight, neonatal intensive care unit admission, gestational hypertension/preeclampsia, and cesarean delivery. The interaction between GA at treatment initiation (stratified as 24-26, 27, 28, 29, and >= 30 weeks of gestation) and treatment group (treated vs routine care), with the outcomes of interest, was used to determine whether GA at treatment initiation was associated with outcome differences. RESULTS: Of 958 women whose cases were analyzed, those who initiated treatment at an earlier GA did not gain an additional treatment benefit compared with those who initiated treatment at a later GA (probability value for interaction with the primary outcome, .44). Similarly, there was no evidence that other outcomes were improved significantly by earlier initiation of GDM treatment (large for GA, P =.76; neonatal intensive care unit admission, P =.8; cesarean delivery, P =.82). The only outcome that had a significant interaction between GA and treatment was gestational hypertension/preeclampsia (P =.04), although there was not a clear cut GA trend where this outcome improved with treatment. CONCLUSION: Earlier initiation of treatment of mild GDM was not associated with stronger effect of treatment on perinatal outcomes.