Subcutaneous administration of GnRH agonist (Triptorelina pamoato 0.1 mg/ml) in the medium-luteal phase (21th day) of the cycle before the stimulation. The next menstruation, in the presence of estradiol level (E2)<30pg/ml and in the absence of follicular cysts, the gonadotropin stimulation was begun. In the presence of at least three follicles of diameter ≥18mm was induced final oocyte maturation by administration of human chorionic gonadotropin (hCG).

GnRH antagonist (cetrorelix acetate 0.25 mg) was administered subcutaneously with a fixed protocol from the day +6 of stimulation or with a flexible protocol from the day in which at least one follicle reached a diameter of 14mm. In both protocols GnRH antagonist was administered until the day of the assumption of hCG. Recombinant Follicle Stimulating Hormone (rFSH) was administered from the 3rd day of menstruation at a dose of 150-300 IU/die according to the characteristics of women. The hCG was administered when at least three follicles had reached 18 mm in diameter and estradiol levels were higher than 150 pg/mL/dominant follicle.

GnRH antagonist (Cetrorelix acetate 0.25 mg) was administered subcutaneously with a fixed or flexible protocol until the day of the assumption of hCG. Corifollitropila alfa was used at dose of 100μg (in women with weight ≤60 kg and age ≤36 years) or 150μg (in women with weight> 60 kg of any age or weight ≥50 kg and age greater than 36 years). Corifollitropina alfa was administered subcutaneously in the day +3 and in the day +5 or +6 was supplemented with rFSH at doses 112-300 IU/day.

The hCG was administered when at least three follicles had reached 18 mm in diameter and estradiol levels were higher than 150 pg/mL/dominant follicle.

the number of total and mature (MII) oocytes retrieved during the pick up.

the number of days since the administration of rFSH o corifollitropina alfa until the administration of hCG

OSI was calculated dividing the total administered FSH dose by the number of retrieved oocytes