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BACKGROUND: Women with ovaries of polycystic morphology (PCO), without any other features of polycystic ovary syndrome (PCOS), respond similarly to women with PCOS when stimulated with exogenous gonadotrophins, and both groups share various endocrinological disturbances underlying their pathology. In women with PCOS, metformin co-treatment during IVF has been shown to increase pregnancy rates and reduce the risk of ovarian hyperstimulation syndrome (OHSS). The aim of this study was to investigate whether metformin co-treatment before and during IVF can also increase the live birth rate (LBR) and lower severe OHSS rates for women with PCO, but no other manifestations of PCOS. METHODS: This study was a double-blind, multi-centre, randomized, placebo-controlled trial. The study population included 134 women with ovulatory PCO (and no evidence of clinical or biochemical hyperandrogenism) undergoing IVF treatment at three tertiary referral IVF units. The primary outcome was LBR. RESULTS: In total, 134 women were randomized, 69 to metformin and 65 to placebo. There were no statistically significant differences between the two groups in baseline characteristics. With regard to IVF outcome, no significant improvements were found in the metformin group when compared with the placebo group. In particular, there was no difference between the groups in rates of live birth [metformin n = 27 (39.1%), placebo n = 30 (46.2), (95% confidence interval 0.38, 1.49, odds ratio = 0.75)], clinical pregnancy [metformin n = 29 (42.0%), placebo n = 33 (50.8%)] or severe OHSS [metformin n = 6 (8.7%), placebo n = 5 (7.7%)]. CONCLUSIONS: There appears to be no benefit in metformin co-treatment before and during IVF in women with PCO without any other features of PCOS. Clinical NCT01046032.

Original publication




Journal article


Hum Reprod

Publication Date





2178 - 2184


Double-Blind Method, Female, Fertilization in Vitro, Humans, Live Birth, Metformin, Ovarian Hyperstimulation Syndrome, Placebos, Polycystic Ovary Syndrome, Pregnancy