In this prospective study, the possible effects of embryo viability and degree of blastocele re-expansion on pregnancy outcomes before vitrified/thawed blastocyst transfer will be evaluated.

Thanks to the advances in embryo vitrification technologies in recent years, high embryo viability can be achieved after thawing, and live birth rates increase after the transfer of these embryos.

Embryo morphology is an essential criterion used to predict embryo viability. Blastocysts endure several morphological challenges during vitrification and thawing, including blastocele collapse, cell collapse, and subsequent rehydration. Blastocysts usually collapse immediately after thawing. Because of these morphological changes, cell damage and loss may occur, and morphological integrity may be impaired.

Considering that implantation results may be affected due to supraphysiological high estrogen and progesterone levels due to multi follicular development in the ovaries during fresh embryo transfers, the study is planned to be conducted only in patients who have undergone artificial endometrial preparation with hormone replacement therapy. Only embryos frozen at the blastocyst stage (day 5) will be included in the study.

After embryo thawing, an experienced embryologist will evaluate embryo viability and expansion and record it in the system. Approximately 2 hours after the indicated procedure (just before embryo transfer), embryo viability and degree of re-expansion will be re-evaluated by the 2nd experienced Embryologist. The evaluation results of both embryologists (embryo viability and re-expansion streams) will be known only to the primary clinician (Assoc. Prof. Şafak Olgan). Pregnancy results will be learned nine days after embryo transfer, In ultrasonography evaluation three weeks after a positive pregnancy result, a clinical pregnancy will be considered in patients with fetal heartbeat, and morphological differences between the pregnant and non-pregnant groups will be evaluated.

Inclusion Criteria:

• Women aged 18-40 years
• Frozen- thawed embryo transfer cycles
• Only the cycles prepared artificially with hormone replacement therapy.
• Embryos with Day 5 (1CC and higher quality)

Exclusion Criteria:

• Embryos at the cleavage stage (D3)
• Patients for whom embryo viability and expansion were not evaluated single-blindly by two different embryologists

Female patients underwent infertility treatment

Women between the ages of 18 and 40 who underwent IVF treatment