Randomized trial of metformin vs insulin in the management of gestational diabetes

To evaluate glycemic control in women receiving metformin or insulin for gestational diabetes, and to identify factors predicting the need for supplemental insulin in women initially treated with metformin.

Women with gestational diabetes who failed to achieve glycemic control with diet and exercise were randomized to receive metformin (n = 47) or insulin (n = 47). Criteria for inclusion were singleton pregnancy, diet, and exercise for a minimum period of 1 week without satisfactory glycemic control, absence of risk factors for lactic acidosis, and absence of anatomic and/or chromosome anomalies of the conceptus. Patients who were lost to prenatal follow-up were excluded.

Comparison of mean pretreatment glucose levels showed no significant difference between groups (P = .790). After introduction of the drug, lower mean glucose levels were observed in the metformin group (P = .020), mainly because of lower levels after dinner (P = .042). Women using metformin presented less weight gain (P = .002) and a lower frequency of neonatal hypoglycemia (P = .032). Twelve women in the metformin group (26.08%) required supplemental insulin for glycemic control. Early gestational age at diagnosis (odds ratio, 0.71; 95% confidence interval, 0.52-0.97; P = .032) and mean pretreatment glucose level (odds ratio, 1.061; 95% confidence interval, 1.001-1.124; P = .046) were identified as predictors of the need for insulin.

Metformin was found to provide adequate glycemic control with lower mean glucose levels throughout the day, less weight gain and a lower frequency of neonatal hypoglycemia. Logistic regression analysis showed that gestational age at diagnosis and mean pretreatment glucose level were predictors of the need for supplemental insulin therapy in women initially treated with metformin.