A meta-analysis of metformin and insulin on maternal outcome and neonatal outcome in patients with gestational diabetes mellitus.

Introduction: The use of metformin for treating gestational diabetes mellitus (GDM) remains controversial because it can pass through the placenta. This meta-analysis aimed to compare the effects of metformin and insulin on maternal and neonatal outcomes in patients with GDM.

Methods: We conducted a comprehensive search of the PubMed, Embase, and Cochrane Library databases, focusing on randomized controlled trials (RCTs) that evaluated the impacts of metformin and insulin on both maternal and neonatal outcomes in patients with GDM.

Results: Twenty-four RCTs involving 4934 patients with GDM were included in this meta-analysis. Compared with insulin, metformin demonstrated a significant reduction in the risks of preeclampsia (RR 0.61, 95% CI 0.48 to 0.78,  < .0001), induction of labor (RR 0.90, 95% CI 0.82 to 0.98,  = .02), cesarean delivery (RR 0.91, 95% CI 0.85 to 0.98,  = .01), macrosomia (RR 0.67, 95% CI 0.53 to 0.83,  = .0004), neonatal intensive care unit (NICU) admission (RR 0.75, 95% CI 0.66 to 0.86,  < .0001), neonatal hypoglycemia (RR 0.55, 95% CI 0.48 to 0.63,  < .00001), and large for gestational age (LGA) (RR 0.80, 95% CI 0.68 to 0.94,  = .007). Conversely, metformin showed no significant impact on gestational hypertension (RR 0.84, 95% CI 0.67 to 1.06,  = .15), spontaneous vaginal delivery (RR 1.13, 95% CI 1.00 to 1.08,  = .05), emergency cesarean section (RR 0.94, 95% CI 0.77 to 1.16,  = .58), shoulder dystocia (RR 0.65, 95% CI 0.31 to 1.39,  = .27), premature birth (RR 0. 92, 95% CI 0.61 to 1.39,  = .69), polyhydramnios (RR 1.11, 95% CI 0.54 to 2.30,  = .77), birth trauma (RR 0.87, 95% CI 0.54 to 1.39,  = .56), 5-min Apgar score < 7 (RR 1.13, 95% CI 0.76 to 1.68,  = .55), small for gestational age (SGA) (RR 0.93, 95% CI 0.71 to 1.22,  = .62), respiratory distress syndrome (RDS) (RR 0.74, 95% CI 0.50 to 1.08,  = .11), jaundice (RR 1.09, 95% CI 0.95 to 1.25,  = .24) or birth defects (RR 0.80, 95% CI 0.37 to 1.74,  = .57).

Conclusions: The findings suggest that metformin can reduce the risk of certain maternal and neonatal outcomes compared with insulin therapy for GDM. However, long-term follow-up studies of patients with GDM taking metformin and their offspring are warranted to provide further evidence.