PROCEDURE
Controlled Ovarian Stimulation + Luteal Phase Support
Short COS protocol with GnRH antagonist followed by progesterone supplementation. Will be initiated after a negative vaginal ultrasonographic scans to define ovarian quiescence, on days 1 and 2 of the menstrual period. For ovarian stimulation, 150-225 UI /day of FSHrec (GONAL F) will be administered along or in combination with 75 UI/day of HMG (Menopur). From day 6 onwards, HMG/FSHrec will be administered on an individual basis according to the serum E2 levels and transvaginal ovarian ultrasound scans and GnRH antagonist (Orgalutran) 0.25 mg /day is introduced as soon as a follicle of 14 mms diameter has achieved. hCGrec (6500 IU, Ovitrelle) will be administered when 7 or 8 follicles with a maximum diameter of \>17-18 mms will observed. 400 mg of micronized vaginal progesterone will be administered (200 mg twice a day vaginal route), during 5 days. An endometrial biopsy and a blood sample will be obtained 7 days after hCG administration (hCH+7)