Impact of Endometrial Compaction on Reproductive Outcomes After Cryotransfer of Euploid Embryos in a Natural Cycle

Inclusion Criteria: * Aged 18 to 50 years * Primary or secondary infertility * Normal uterine cavity * Endometrial preparation in a modified natural cycle for single embryo transfer * Embryo in blastocyst state from own oocyte or oocyte donation cycles, who had normal results on preimplantation genetic testing for aneuploidy (PGT-A) via trophectoderm biopsy. Exclusion Criteria: * Uterine or endometrial disease (multiple myomatosis \[\>3 fibroids of \> 3 cm\], adenomyosis, Asherman syndrome) * Difficulties in correctly measuring endometrial thickness due to a retroverted or tilted uterus * History of recurrent implantation failure (3 or more transferred blastocysts of good quality, from their own oocyte \[\<35 years\] or oocyte donation); recurrent early Pregnancy Loss (the loss of two or more pregnancies before 10 weeks of gestational age. * Suboptimal endometrial response (endometrium \< 6 mm on the day of ovulation triggering).