Effect of blastocyst quality on human sex ratio at birth in a single blastocyst frozen thawed embryo transfer cycle

Abstract

Research question To determine whether blastocyst quality affects the sex ratio at birth through a single blastocyst frozen - thawed embryo transfer (SBFET) cycle.Design In this retrospective analysis, we examined 3,041 singleton infants born following SBFET between 2017 and 2020 at a single institution. We compared the sex ratios of these infants with respect to the blastocyst quality, embryo growth rate, and morphology.Results The main outcomes of this study were that the sex ratio (M/F) at birth of SBFET was 1.24. Mothers >40 years old had a considerably lower sex ratio than mothers <40 years old (0.39 vs. 1.23–1.28, p < .05). Transplanting high-quality blastocysts significantly increased the proportion of boys born (1.29 vs. 0.88, p < .05). There were no significant differences in the sex ratio with respect to the inner cell mass (ICM) score and expansion degree. Additionally, a high trophoblastic cell (TE) score resulted in a significantly higher sex ratio than the TE score with C (1.62 vs. 1.15 vs. 0.85, p < .001). Multivariable logistic regression analysis was performed to determine which variables were significant factors affecting sex ratio, and the outcomes were consistent with previous findings.Conclusions Our study indicated that high-quality, especially good TE score, had a higher chance of resulting in a male infant than a female infant.

Keywords

• Secondary sex ratio
• blastocyst quality
• trophectoderm
• inner cell mass
• single blastocyst frozen thawed embryo transfer