Impact of IVF Hormonal Therapy on Endometrial Receptivity and Endometrial Senescent Cell Pathological Accumulation

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)

6 mg of oestradiol orally administered starting the first day of the menstrual period, followed by an endometrial scan 10-days later, and when a 7 mms triple line endometrium has seen by vaginal ultrasound scan, 800 mg of micronized vaginal progesterone (400 mg twice a day vaginal route), during five days, will be added to the oestrogen therapy. An endometrial biopsy and a blood sample will be obtained on day 5 of progesterone administration (P+5)

No hormonal stimulation. From day 6 of the menstrual period, follicular growth will be evaluated. As soon as a follicle reaches 17mm in diameter, ovulation test strips will be provided to assess LH levels in the first morning urine. The participant will report the positive and will be scheduled for sampling seven days later. An endometrial biopsy and a blood sample will be obtained 7 days after LH peak (LH+7)

Recruited among women belonging to the oocyte donation program and will follow the procedures described above for the Natural Cycle group. No hormonal stimulation. From day 6 of the menstrual period, follicular growth will be evaluated. As soon as a follicle reaches 17mm in diameter, ovulation test strips will be provided to assess LH levels in the first morning urine. The participant will report the positive and will be scheduled for sampling seven days later. An endometrial biopsy and a blood sample will be obtained 7 days after LH peak (LH+7)