Background:  There are differences in opinion as to whether metformin should play a role in the primary treatment of anovulatory infertility for women with polycystic ovary syndrome (PCOS).
Aim:  The aim of this study was to ascertain the best available evidence comparing metformin versus clomiphene treatment for non‐obese women with anovulatory infertility related to PCOS.
Methods:  Meta‐analysis of available data from randomised controlled trials that examined metformin versus clomiphene for the subgroup of women in the lower body mass index (BMI) range (primarily non‐obese). Primary outcomes were clinical pregnancy and live birth.
Results:  For women with BMI ≤ 30–32 kg/m2, clinical pregnancy rates were 36.7% (52/142) for metformin and 35.7% (51/143) for clomiphene; live birth rates were 30.3% (43/142) for metformin and 30.8% (44/143) for clomiphene.
Conclusion:  The available randomised trial data show no significant difference in effectiveness of metformin versus clomiphene as ovulation induction agents for non‐obese women with anovulatory PCOS. Metformin and clomiphene are both suitable options for first‐line treatment.