Effectiveness of Metformin in the Prevention of Gestational Diabetes Mellitus in Obese Pregnant Women.

OBJECTIVE:  To assess the effectiveness of metformin in the incidence of gestational diabetes mellitus (GDM) in obese pregnant women attending a public maternity hospital in Joinville, Santa Catarina, Brazil.

METHODS:  Randomized clinical trial including obese pregnant women with a body mass index (BMI) ≥ 30 kg/m2 , divided into two groups (control and metformin). Both groups received guidance regarding diet and physical exercise. The participants were assessed at two moments, the first at enrollment (gestational age ≤ 20) and the second at gestational weeks 24-28. The outcomes assessed were BMI and gestational diabetes mellitus (GDM) diagnosis. The data distribution was assessed with the Friedman test. For all the analytical models, the p -values were considered significant when lower than 0.05. The absolute risk reduction was also estimated.

RESULTS:  Overall, 164 pregnant women were assessed and further divided into 82 participants per group. No significant difference was observed in BMI variation between the control and metformin groups (0.9 ± 1.2 versus 1.0 ± 0.9, respectively, p  = 0.63). Gestational diabetes mellitus was diagnosed in 15.9% ( n  = 13) of the patients allocated to the metformin group and 19.5% ( n  = 16) of those in the control group ( p  = 0.683). The absolute risk reduction was 3.6 (95% confidence interval 8.0-15.32) in the group treated with metformin, which was not significant.

CONCLUSION:  Metformin was not effective in reducing BMI and preventing GDM in obese pregnant women.