Background: Insulin resistance is common in women with Polycystic Ovary Syndrome (PCOS) and can cause poor outcome of infertility treatment. The aim of our study was to assess the effect of treatment with metformin on outcome of Intra Cytoplasmic Sperm Injection (ICSI) in infertile PCOS women.

Methods: A randomized clinical trial study was carried out in infertile women with PCOS, before ICSI, referred to infertility clinic of Mirza Koochackhan Hospital of Tehran University of Medical Science Tehran, Iran, between 2006 and 2008. The patients were randomized in two groups of metformin 500 mg Po, three times daily, six weeks before the ICSI cycle and placebo patients in each group were divided into BMI <28 kg/m² and BMI ≥28 kg/m².

Results: Of 52 study women 26(50%) were in metformin group. mean age were 29.8±4.9 year in metformin group versus 29.4±5.9 year and placebo groups. Treatment with metformin, in subgroup of BMI <28 kg/m², significantly increased number of mature follicle (p=0.01), embryo (p=0.04), oocytes (p=0.007) and mature oocytes (p=0.03) but in subgroup of BMI≥28 kg/m², there was no significant difference in the metformin and placebo groups (p>0.05). Metformin treatment caused more chemical and clinical pregnancy rates, and less abortion rate in overweight and normal patients, but the differences were not significant (p>0.05). Logestic regression analysis showed, adjusting number of mature follicle, number of embryos, quality of embryos, oocytes and BMI and treatment showed no significant effect on clinical pregnancy rates (p>0.05).

Conclusions: Among normal weight PCOS women, effect of treatment with metformin is better than overweight PCOS women. However further studies are needed.