['Low-grade chronic inflammation, evaluated by serum C-reactive protein (CRP) levels, has been connected with the polycystic ovary syndrome (PCOS). Effects of metformin on CRP before and during IVF treatment in women with PCOS are unknown.', 'A prospective double-blind placebo-controlled study.', 'Single-center IVF clinic.', 'Sixty-three PCOS women.', 'Treatment with 2000 mg/day metformin or identical placebo tablets for at least 14 weeks before and then during IVF treatment, ending on the day of hCG injection.', 'The CRP levels at five time points ending on the day of ovum collection.', 'At inclusion of infertile untreated PCOS women, body mass index associated with CRP in multivariable regression analysis (r = 0.18). Androgen levels did not associate with CRP levels. Metformin did not influence CRP levels during pretreatment or IVF cycle. After hCG injection, CRP increased in both the metformin and the placebo groups with no significant difference between the groups.'] Are c-reactive protein levels unaffected by metformin during pretreatment and an IVF cycle in women with polycystic ovary syndrome?