Role of Metformin in the Treatment of Gestational Diabetes

OBJECTIVE: To evaluate the safety and efficacy of metformin in the treatment of gestational diabetes mellitus (GDM). DATA SOURCES: A literature search was conducted via PubMed (1948-December 2008), International Pharmaceutical Abstracts (1970-December 2008), and Cochrane Library (up to 2008) using the search terms gestational diabetes and metformin. No limits were applied to the search. Reference citations from relevant publications identified were also reviewed. STUDY SELECTION AND DATA EXTRACTION: All articles identified from the data sources were reviewed for inclusion. Original research and retrospective cohorts were included in the review. Thirty-three articles were selected for review; 6 met the inclusion criteria. Trials evaluating the use of metformin in pregnant women with polycystic ovarian syndrome were not included. DATA SYNTHESIS: Metformin has been found largely to be effective in the treatment of GDM. One retrospective study reported that preeclampsia and neonatal mortality are increased with the use of metformin. The largest randomized trial to date found that neonatal and maternal complications did not differ between patients treated with metformin and those treated with insulin; however, rates of preterm birth were increased in the metformin group. In all studies reviewed, patients treated with metformin tended to be overweight or obese and required varying doses of metformin. CONCLUSIONS: Metformin appears to be effective for the treatment of GDM, but safety concerns may limit its use. Due to these concerns, insulin should remain the drug of choice if dietary measures alone fail.