The study was organised on an outpatient basis. All subjects underwent COS according to centre´s standard protocol (but Luveris) when a GnRH antagonist was going to be used. The COS was started on day 2-3 of the cycle with an initial dose of follitropin alfa ranging from 225 to 450 IU/day depending on subjects' baseline profile. Then the daily dose was adjusted according to ovarian response. When detected a follicle ≥ 14 mm or serum E2 levels > 200 pg/ml, then both 0.25 mg/day of Cetrotide and 150 IU/day of Luveris were initiated. Randomisation to Luveris supplementation or not took place at any time between the fourth day of COS (S4) and the first dose of Cetrotide, which were administered in the morning. Once COS completed, follitropin alfa, lutropin alfa, and Cetrorelix were stopped and recombinant-human choriogonadotropin (r-hCG) administered within the following 24 hours. Standard criteria for r-hCG administration were the presence of at least of one follicle ≥18 mm and two addition follicles > 16 mm together with appropriate E2 levels for the follicular number and size.