ABSTRACT
Objective: To investigate the effect of embryo quality at different developmental stages on the secondary sex ratio (SSR) of single live birth neonates. Methods: Data for patients with singleton live births after embryo transferred between January 2016 and January 2022 were retrospectively analyzed. The effect of embryo quality at different development stages on the SSR of 11 713 singleton live births were investigated. The association of SSR and embryo quality at different development stages was examined in univariate analysis and in a multivariate logistic regression model, after adjustment for confounders, using two models (Ⅰ and Ⅱ). Results: The age of both male and female, body mass index of both male and female, basal follicle stimulating hormone and estradiol, smoking of male, methods of insemination, methods of sperm extraction, types of transfer cycle and the number of embryo transferred were not related with SSR (all P>0.05). After adjustment for confounders, the probability of a male live birth was higher after transfer of good-quality blastula than after transfer of poorer-quality blastula (model Ⅰ: aOR=0.73, 95%CI: 0.65-0.82, P<0.001; model Ⅱ: aOR=0.73, 95%CI: 0.65-0.82, P<0.001). The quality of cleavage stage embryo was not associated with SSR (model Ⅰ: aOR=0.99, 95%CI: 0.87-1.13, P=0.937; model Ⅱ: aOR=0.99, 95%CI: 0.87-1.13, P=0.899). Conclusions: The SSR of singleton live births after embryo transfer is not correlated with the quality of cleavage stage embryo, but is correlated with the quality of blastula. Good-quality blastula transfer is more likely to result in a male live birth.