This project seeks to demonstrate the clinical value of the personalised diagnosis of the endometrial factor in infertility.

This project seeks to investigate differences in implantation (IR), pregnancy (PR), ongoing pregnancy (OP) rates, miscarriages, deliveries (LB) and obstetrical, delivery and neonatal outcomes among women undergoing IVF treatment with own oocytes, at first site appointment (up to 3 previous implantation failures in other sites) and blastocyst stage (day 5 or 6). Patients are allocated through computer-generated randomization into one of the three groups: Fresh embryo transfer (ET), Frozen embryo transfer (FET) or personalized embryo transfer (pET) after identification of the personalized window of implantation using the endometrial receptivity analysis (ERA) test, all of them following the usual clinical practice in a same-cycle embryo transfer.

A total of 546 infertile women under 38 years old undergoing her first IVF/ICSI cycle with elective blastocyst transfer are randomized in this prospective, multicenter, open label and controlled trial.

Inclusion Criteria:

1. Patients indicated to undergo a cycle of IVF/ICSI with their own oocytes.
2. Age ≤ 37 years
3. BMI: 18.5 to 30
4. Normal ovarian reserve (AFC ≥ 8; FSH < 8)
5. The most appropriated stimulation protocol will be decided by their doctor.
6. Blastocyst transfer (on day 5 or 6)
7. Blastocyst vitrification with open protocols (Cryotop, Cryoleaf, or Cryolock) or closed protocols (Cryotip or CBSStraw.)
8. Any pathology affecting the endometrial cavity such as polyps/sub-mucosal myomas, intramural myomas > 4 cm, or hydrosalpinx affecting the endometrial cavity must be previously operated.

Exclusion Criteria:

1. Patients with recurrent miscarriages (> 2 previous biochemical pregnancies or > 2 spontaneous miscarriages)
2. Patients with a severe male factor (spermatozoa < 2 million/ml)
3. Patients with implantation failure (>3 failed cycles with good quality embryos)

Post-Randomization Exclusion Criteria:

1. Endogenous progesterone level ≥ 1,5 ng/ml at the day of hCG administration in all groups.
2. Absence of blastocysts (day 5 or 6) for embryo transfer.
3. Risk of ovarian hyperstimulation syndrome in any of the three groups and therefore a clinical indication to cancel the transfer cycle where the stimulated patient is from group A (ET).

Note: PGT-A is not an inclusion criteria neither an exclusion criteria, therefore those cycles in which PGT-A was performed will be included

Women undergoing IVF treatment