Impact of single blastocyst selection strategy on pregnancy outcomes in frozen embryo transfer

This study aimed to evaluate the impact of cleavage stage embryo ratings on pregnancy outcomes following frozen embryo transfer (FET) and their correlation with blastocyst grades.

A retrospective cohort study was conducted on 854 FET cycles from January 2018 to August 2024. Participants were women undergoing FET with cryopreserved embryos. Exclusion criteria included multiple initial in vitro fertilization (IVF) attempts, advanced age, chromosomal abnormalities, and uterine anomalies. Embryo quality was assessed at the cleavage and blastocyst stages, and FET protocols were tailored to each patient. The primary outcome was clinical pregnancy rate, defined by ultrasound-detected fetal heartbeat. Data was analyzed using SPSS 19.0, with logistic regression to adjust for confounders.

The overall pregnancy rate was 53.98% (461/854). Significant differences in pregnancy rates were observed among blastocyst grades, with Grade 1 achieving the highest rate (60.37%). Lower cleavage stage embryo grades (Grade 3 and Grade 4) were associated with reduced pregnancy odds (OR = 0.63 and OR = 0.50, respectively, p < 0.05). Other factors influencing pregnancy outcomes included female age and anti-Müllerian hormone (AMH) levels. The study underscores the importance of cleavage stage embryo ratings, particularly for Grade 2 embryos, in the context of FET procedures using ovulation induction cycle (OIC) and intracytoplasmic sperm injection (ICSI).

Cleavage stage embryo ratings significantly affect pregnancy outcomes following FET. Higher ratings correlate with better pregnancy rates, highlighting the importance of comprehensive embryo quality assessment.