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Metformin Use in Gestational Diabetes

Mar 14, 2006

Although the use of metformin in gestational diabetes is not yet accepted as treatment in gestational diabetes, evidence is accumulating that it may be a useful treatment. The prevalence of Type 2 diabetes in women of childbearing age continues to grow as the incidence of Type 2 diabetes increases. Recent evidence shows that treatment of gestational diabetes ensures the best possible outcome for pregnancy complicated by gestational diabetes. Metformin is a logical treatment in these circumstances but there has always been concern about its safety for the fetus, particularly as it crosses the placenta and it may increase the risk of teratogenesis. Although evidence is accumulating that metformin is useful and has a role in polycystic ovary syndrome, a condition of insulin resistance, it is not yet accepted as treatment for Type 2 diabetes in pregnancy and gestational diabetes.

Observational data supports the use of metformin in Type 2 diabetes in pregnancy and its role in gestational diabetes is currently under investigation. Metformin may become an important treatment for women with either gestational or Type 2 diabetes in pregnancy and indeed may have additional important benefits for women, including reducing insulin resistance, body weight and long-term risk of diabetes.


To review pregnancy outcomes in women with Type 2 diabetes (Type 2 DM), comparing women treated with those not treated with metformin. Methods Data were collected by case-note review for all pregnancies in women with Type 2 DM over a 6-year period (1998-2003) at the National Women’s Hospital. Two hundred and fourteen pregnancies were included, metformin was taken in 93 pregnancies and continued until delivery in 32; the remaining 121 pregnancies comprised the control group. The principal outcome measures were preeclampsia, perinatal loss and neonatal morbidity. Results Baseline characteristics differed between groups: women in the metformin group had greater mean (sd) body mass index [35.5(7.6) vs. 33.5(6.6) kg/m(2), P < 0.05], more chronic hypertension (19% vs. 7%, P < 0.05) and higher mean (sd) first trimester glycated hemoglobin (HbA(1c)) levels [8.3(1.9)% vs. 7.5(1.7)%, P < 0.005]. There was no difference between metformin and control groups, respectively, in the rate of preeclampsia (13% vs. 14%, P = 0.84), perinatal loss (3% vs. 2%, P = 0.65) or neonatal morbidity, including rate of prematurity (23% vs. 22%, P = 0.7), admission to the neonatal unit (40% vs. 48%, P = 0.27), respiratory distress (9% vs. 18%, P = 0.07) and treatment with intravenous dextrose (20% vs. 31%, P = 0.08).

From the results it was concluded that pregnant women with Type 2 DM who were treated with metformin had more risk factors for adverse pregnancy outcomes, but no differences in outcomes were seen compared with women not taking metformin.
There is a need for a randomized controlled trial in women with Type 2 diabetes in pregnancy with long-term follow-up of both mothers and children. Until then the best advice remains that optimized glycemic control prior to conception and during pregnancy is the most important intervention for best possible pregnancy outcome.

Diabet Med. 2006 Mar;23(3):318-22. Diabet. Med. 23, 318 -322 (2006).


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