Metformin may be better than insulin for the treatment of gestational diabetes

Reference

Picon-Cesar MJ, Molina-Vega M, Suarez-Arana M, et el. Metformin for gestational diabetes study: metformin vs insulin in gestational diabetes: glycemic control and obstetrical and perinatal outcomes: randomized prospective trial. Am J Obstet Gynecol 2021;225(5):517e.1-17.

Synopsis

This study, conducted in 2 academic medical centers in Spain, was a relatively small (N = 196) open-label randomized controlled trial of metformin (MET) versus insulin (INS) for the treatment of gestational diabetes. Targets for glycemic control were 70 mg/dL to 95 mg/dL fasting, and not more than 140 mg/dL 1 hour postprandial. If women had 2 or more glucose measurements weekly above the target ranges, their gestational diabetes was considered uncontrolled. Women who failed a trial of lifestyle modification for glycemic control were eligible if they were aged 18 years to 45 years and had a singleton pregnancy at 14 to 35 weeks' gestational age. Women were excluded if their fasting glycemia was greater than 120 mg/dL, or if they had gastrointestinal diseases. The authors didn’t provide a description of randomization methodology. Women in the MET group initialized treatment with 425 mg to 850 mg daily in 1 or 2 doses and titrated as needed to a maximum of 2550 mg daily. Women in the INS group started with detemir insulin 0.2 IU/kg with or without mealtime aspartame insulin. Women who did not achieve glycemic control on the maximum dose of MET (20/97 [21%]) received INS in addition to the MET, as needed, to achieve glycemic control; they required less insulin on average than the INS group. Those patients were analyzed by intention to treat in the MET group. Four women switched from MET to INS due to gastrointestinal side effects. There were no significant differences between the groups for measures of glycemic control, including HbA1c. Most obstetric and perinatal outcomes were not significantly different between groups, including hypertensive disorders, preterm births, gestational age at delivery, and multiple perinatal outcomes. Induction of labor was less frequent in the MET group than in the INS group (46% vs 63%; odds ratio [OR] 0.51; 95% CI 0.28 - 0.90; P = .029; number needed to treat [NNT] = 6; 3 - 51). Cesarean delivery was also less frequent in the MET group (28% vs 53%; OR 0.345; 0.19 - 0.63, P = .001; NNT = 4; 3 - 9). These differences were not accompanied by differences in fetal macrosomia or large or small for gestational age. Hypoglycemic events were more frequent in the INS group (56% vs 18%; OR 6.12; 3.13 - 11.94; P = .000). Weight gain was lower on average among women treated with MET from randomization to 36 to 37 weeks (3.9 vs 1.4 kg; P = .000). Women in the MET group were also more likely to choose the same treatment in the future (70% vs 32%; P=.000).