Rate and Characteristics of Metformin Use in Gestational Diabetes.

OBJECTIVE: To determine the rate and characteristics of metformin use in the treatment of gestational diabetes mellitus (GDM). METHODS: A total of 286 pregnant women diagnosed with GDM at a university-based tertiary care hospital were included. In addition to nutritional therapy, the decision regarding metformin use was at the physicians' discretion. Data were retrieved from medical records, including baseline obstetric characteristics, GDM diagnosis, dosage and formulation of metformin, insulin requirement, and pregnancy outcomes. The rate of metformin use was estimated, and factors associated with metformin use were evaluated. RESULTS: The mean age was 33.8 years, 55.9% were nulliparous, and 43.4% were overweight or obese. Mean gestational age at diagnosis was 18.7 weeks, and 57% were diagnosed before 20 weeks. Metformin was used in 16.1%, with an initial dosage of 500-1000 mg/d in 95.7%. The final dosage was > 1000-2000 mg/d in 43.5%. A dosage increment was required in 50%. Insulin therapy was needed in 13% of those who received metformin. Metformin use significantly increased in those with obesity, high 50-g glucose challenge test results, and abnormal fasting plasma glucose (FPG) at diagnosis. Logistic regression analysis showed that the only factors that significantly increased the use of metformin therapy were obesity (adjusted OR: 2.88, 95% CI: 1.17-7.07, p = 0.021) and abnormal FPG at diagnosis (adjusted OR: 5.06, 95% CI: 2.21-11.57, p < 0.001). Maternal and neonatal outcomes were comparable between those with and without metformin use. CONCLUSION: Metformin was used in 16.1% of women with GDM. Significant associated factors were obesity and abnormal FPG at diagnosis.