The quality of evidence is downgraded by study limitations (unclear allocation concelament and lack blinding in half of the studies) and by imprecise results (few patients and outcome events).
A Cochrane review «Metformin during ovulation induction with gonadotrophins followed by timed intercourse or intrauterine insemination for subfertility associated with polycystic ovary syndrome»1 «Bordewijk EM, Nahuis M, Costello MF et al. Metformin during ovulation induction with gonadotrophins followed by timed intercourse or intrauterine insemination for subfertility associated with polycyst»1 included 5 studies with a total of 264 subjects comparing gonadotrophins plus metformin versus gonadotrophins in anovulation due to polycystic ovary syndrome (PCOS). The gonadotrophin used was recombinant follicle stimulationg hormone (FSH) in 4 studies and highly purified FSH in 1 study. Metformin plus FSH was associated with a higher live birth rate when compared with FSH (table «Gonadotrophins plus metformin versus gonadotrophins for subfertility»1). This suggests that if the chance of live birth after FSH is assumed to be 27%, then the chance after addition of metformin would be between 32% and 60%. There were no difference in rates of multiple pregnancy, miscarriage, or ovarian hyperstimulation syndrome.
| Outcome | Relative effect (95% CI) OR | Assumed risk - Gonadotrophins plus placebo | Intervention - Gonadotrophins plus metformin | Number of participants (studies) |
|---|---|---|---|---|
| Live birth rate Follow-up: 3-6 months | 2.31 (1.24 to 4.33) | 267 per 1000 | 457 per 1000, 190 more per 1000 (42 to 345) | 180 (2) |
| Multiple pregnancy rate | 0.55 (0.15 to 1.95) | 52 per 1000 | 26 per 1000, 23 fewer per 1000 (44 fewer to 25 more) | 232 (4) |
| Ongoing pregnancy rate | 2.46 (1.36 to 4.46) | 217 per 1000 | 393 per 1000, 189 more per 1000 (57 to 336) | 232 (4) |
| Clinical pregnancy rate | 2.51 (1.46 to 4.31) | 252 per 1000 | 444 per 1000, 206 more per 1000 (78 to 340) | 264 (5) |