Effect of blastocyst quality on neonatal outcomes in frozen embryo transfer cycles: a cohort study.

PURPOSE: To study the effect of blastocyst quality on neonatal outcomes in frozen embryo transfer (FET) cycles. METHODS: This retrospective study included a total of 7,308 women who underwent single blastocyst transfer during FET cycles and achieved singleton live births from January 2015 to June 2022. Women were categorized into two groups: poor-quality blastocyst (PQB; n = 2540) and good-quality blastocyst (GQB; n = 4768). The primary outcomes were the rates of cesarean section and male sex. The second outcomes were very small for gestational age (VSGA), small for gestational age (SGA), large for gestational age (LGA), very large for gestational age (VLGA), very preterm birth (VPTB), preterm birth (PTB), high birth weight (HBW), very low birth weight (VLBW), low birth weight (LBW), gestational age, and birth weight. RESULTS: Compared with the PQB group, the GQB group was associated with a decreased cesarean section rate (adjusted odds ratio [aOR] 0.88, 95% confidence interval [CI], 0.77-0.99; P = 0.034) and an increased likelihood of having a male child (aOR 1.27, 95%CI, 1.14-1.40; P < 0.001). However, no differences were observed in other neonatal outcomes, including VSGA, SGA, LGA, VLGA, VPTB, PTB, HBW, VLBW, LBW, gestational age, and birth weight. CONCLUSIONS: GQB is associated with a decreased cesarean section rate and an increased likelihood of having a male child. However, it has no effect on other neonatal outcomes. Therefore, both clinicians and patients can be reassured about the neonatal outcomes of singleton live births resulting from PQB in FET cycles.