- Sample size calculation: To detect a difference from 40 to 60% (Relative risk: 1.50) on pregnancy rate (PR) between patients with low and high androgen levels with respect to the mean of each COS protocol, with a confidence level of 95% (error α=0.05) and 80% of power (error β=0.2), 97 patients per arm were needed. (n=388 patients). Rounding up, 400 patients are to be recruited.