Introduction: Maternal overweight and obesity is associated with well-recognised pregnancy complications. Our aim was to evaluate the role of metformin in addition to dietary and lifestyle advice for pregnant women who were overweight or obese.
Methods: We conducted a double blind, placebo controlled, randomised trial. Eligible women with a live singleton pregnancy between 10+0 and 20+0 weeks gestation, and were overweight or obese (BMI ≥25.0 kg/m2) at their first prenatal visit were recruited from public maternity hospitals in Adelaide, South Australia.
All women received an antenatal dietary intervention and were randomly allocated to receive either metformin to a maximum dose of 2000mg per day, or an identical appearing placebo.
The primary outcome was the proportion of infants with birth weight >4000grams. Secondary outcomes included gestational weight gain (GWG), maternal pregnancy, labour and birth, and infant outcomes. Statistical analyses adopted intention to treat principles.
Results: 524 women were randomized (261 Metformin; 263 Placebo). There was no significant difference in the proportion of infants with birth weight >4000g (15.63% Metformin versus 14.34% Placebo; aRR 0.97; 95% CI 0.65-1.47; p=0.899). Women receiving metformin had lower weekly GWG (0.38+0.34kg Metformin vs 0.47+0.35kg Placebo; aMD -0.08; 95% CI -0.14--0.02; p=0.007), and were more likely to gain below the Institute of Medicine recommendations (39.2% Metformin vs 27.0% Placebo; aRR 1.46; 95% CI 1.10-1.94; p=0.008). Total GWG was not statistically significantly different (7.48+6.95kg Metformin versus 8.72+6.91kg Placebo; aMD -1.18; 95% CI -2.37 to 0.01; p=0.053). There was no evidence of impact on pregnancy and birth outcomes.
Conclusion: There was some evidence that metformin as an adjuvant therapy to a dietary and lifestyle intervention in overweight and obese pregnant women reduced GWG measures, but there was no evidence of an impact on pregnancy and birth outcomes.