Prevention of gestational diabetes mellitus by continuing metformin therapy throughout pregnancy in women with polycystic ovary syndrome

The aim of the present study was to assess whether continuation of metformin therapy throughout pregnancy can reduce the development of gestational diabetes in women with polycystic ovarian syndrome (PCOS). This experimental study was conducted in a private tertiary level infertility care center between June 2002 and December 2006. Fifty-nine non-diabetic PCOS patients who conceived while taking metformin and different ovulation-inducing agents comprised the sample group. Twenty-nine of them continued metformin throughout pregnancy and 30 did not. The main outcome measure was development of gestational diabetes in women with PCOS and their fetal outcome. Basic parameters such as age, body mass index, levels of follicle-stimulating hormone and luteinizing hormone, free testosterone, dihydroepiandrosterone sulfate, fasting sugar and fasting insulin did not differ between the two groups. Among 29 women who received metformin, gestational diabetes developed during one of 29 pregnancies (3.44%) versus nine of 30 pregnancies (30%) without metformin. The odds ratio for gestational diabetes in women without metformin versus with metformin was 12 (95% confidence interval: 6.20-18.08). All babies born in the metformin group had average birthweight and those in the control group 4 (13.33%) were large for date. In PCOS use of metformin throughout pregnancy is associated with and might be responsible for a ninefold reduction (30-3.44%) of gestational diabetes.