A Cochrane review included 9 studies with a total of 816 subjects. Metformin treatment before or during assisted reproductive technique cycles (in vitro fertilisation, IVF or intra-cytoplasmic sperm injection, ICSI) compared to placebo or no treatment did not improve live birth rate (OR 1.39, 95% CI 0.81 to 2.40; 5 trials, n=551, I² 52%, low-quality evidence). This suggests that for a woman with a 32 % chance of achieving a live birth using placebo, the corresponding chance using metformin treatment would be between 28% and 53%. When metformin was compared with placebo or no treatment, clinical pregnancy rates were higher in the metformin group (OR 1.52; 95% CI 1.07 to 2.15; 8 RCTs, n=775, I²=18%, moderate-quality evidence). The risk of ovarian hyperstimulation syndrome in women with PCOS and undergoing IVF or ICSI cycles was reduced with metformin (OR 0.29; 95% CI 0.18 to 0.49, 8 RCTs, n=798, women, I²=11%, moderate-quality evidence). This suggests that for a woman with a 27% risk of having OHSS without metformin the corresponding chance using metformin treatment would be between 6% and 15%.
Comment: The quality of evidence is downgraded by several issues in study quality and by imprecise results (few patients and wide confidence intervals).