Prevention of gestational diabetes by metformin plus diet in patients with polycystic ovary syndrome

ObjectiveTo prospectively assess whether metformin diet safely provides primary and secondary prevention of gestational diabetes (GD).DesignAssess development of GD on metformin diet.SettingOutpatient clinical research center.Patient(s)One hundred forty-two nondiabetic women with polycystic ovary syndrome (PCOS) who had at least one live-birth (LB) pregnancy on metformin diet (172 pregnancies, 180 LBs).Intervention(s)Women were given 26% protein, 44% carbohydrate diets, without calorie restriction during pregnancy. Metformin (2–2.55 g/d) was given preconception, through pregnancy.Main Outcome Measure(s)Development of GD.Result(s)On metformin, GD developed in 12 (7%) of 172 LB pregnancies. Forty-seven women had at least one previous LB pregnancy (n = 64) without metformin, with GD developing in 19 (30%). Subsequently, on metformin, these 47 women had 50 LB pregnancies, developing GD in 6 (12%), which was a statistically significant difference. Of 15 women who had previous GD without metformin, GD developed in 5 (31%) of 16 subsequent pregnancies on metformin. Of 32 women who were previously free of GD without metformin, GD developed in 1 (3%) of 34 subsequent pregnancies on metformin. Previous GD without metformin was the only statistically significant explanatory variable for current GD on metformin.Conclusion(s)Metformin diet during pregnancy in women with PCOS facilitates primary and secondary prevention of GD.