The effects of metformin treatment of gestational diabetes on maternal weight and glucose tolerance postpartum--a prospective follow-up study.

INTRODUCTION

Metformin seems to reduce gestational weight gain compared with insulin in women with gestational diabetes (GDM). Women with GDM requiring insulin are more likely to develop abnormal glucose tolerance postpartum than women treated with diet only. In this prospective follow-up study of a randomized clinical trial, we investigated the effect of metformin treatment in women with GDM on weight gain and glucose tolerance postpartum.

MATERIALS AND METHODS

Women with GDM with two or more pathologic glucose values at 2-h 75-g oral glucose tolerance test (OGTT) were recruited. Those needing medication to achieve sufficient glycemic control were randomized at 22-34 weeks of gestation to either metformin (n = 110) or insulin (n = 107) treatment until delivery. A third GDM group (n = 128) requiring no medication had only diet treatment. Weight, OGTT and glycosylated hemoglobin (HbA1c) were determined at 6-8 weeks and 1 year postpartum.

RESULTS

At least one postpartum visit was attended by 104, 101 and 120 women in the metformin, insulin and diet-only groups, respectively. No significant differences were found in the change of weight, HbA1c or OGTT glucose values between the groups during the study (p ≥ 0.121 in all comparisons). One year postpartum the diet-only group had less impaired glucose tolerance compared with the metformin and insulin groups (7.1%, 19.1% and 15.6%, respectively; overall p = 0.039) and a lower incidence of diabetes (p = 0.027).

CONCLUSIONS

Short-term metformin therapy does not affect weight, HbA1c or OGTT glucose values postpartum compared with insulin or diet-only treatments. Women with GDM requiring no medication are least likely to develop impaired glucose tolerance or diabetes postpartum.