Metformin and gonadotropins for ovulation induction in patients with polycystic ovary syndrome: a systematic review with meta-analysis of randomized controlled trials

The current systematic review with meta-analysis of randomized controlled trials (RCTs) was aimed to evaluate the effects of metformin on reproductive outcomes in patients with polycystic ovary syndrome (PCOS) who receive gonadotropins for ovulation induction. After systematic review of electronic databases and websites for registration of RCTs, a total of 7 RCTs reporting data on 1023 cycles were included in the final analysis. Descriptive data showed an overall low studies' quality due to unclear sequence generation and allocation concealment, lack of blinding procedure, incomplete outcome data and several biases and/or confounders. Data synthesis showed that metformin improved live-birth (odds ratio [OR] = 1.94, 95% confidence interval [CI] 1.10 to 3.44; P = 0.020) and pregnancy (OR = 2.25, 95% CI 1.50 to 3.38; P < 0.0001) rates, without significant heterogeneity across the studies (P = 0.230, estimation of inconsistency = 30%; and P = 0.710, estimation of inconsistency = 0%, respectively, for live-birth and pregnancy rates). A significant reduction of cancellation rate was observed after metformin administration (OR = 0.41, 95% CI 0.24 to 0.72, P = 0.002) without significant heterogeneity across the studies (P = 0.500, estimation of inconsistency = 0%). Metformin administration influenced or did not influence other secondary endpoints assessed with a significant heterogeneity. In conclusion, metformin administration increases the live-birth and pregnancy rate in PCOS patients who receive gonadotropins for ovulation induction. Further well designed, blinded, placebo-controlled, and adequately powered RCTs are need to confirm that metanalytic results.