Objective:To explore the influencing factors of the secondary sex ratio (SSR) of singleton babies born following assisted reproductive technology.Methods:A total of 7020 single babies delivered by assisted reproductive technology at the Reproductive Medicine Center of the First Affiliated Hospital of USTC (Anhui Provincial Hospital) from January 2000 to December 2018 were collected in a retrospective cohort study. The effect of influencing factors, such as maternal age, fertilization method, embryo transfer type and embryo transfer period on the sex of singleton babies were analyzed.Results:Among 7020 babies, 3730 were boys and 3290 were girls. The total SSR was 113∶100. The SSR of in vitro fertilization (IVF) was significantly higher than that of intracytoplasmic sperm injection (ICSI) fertilization (121∶100 vs. 95∶100, P<0.001), while other factors had no significant effect on the SSR of infants born. In the stratified analysis, there was no difference in SSR between IVF and ICSI in the blastocyst embryo transfer group with mother's age 35 years or older ( P<0.05), while the SSR of IVF in the other groups was higher than that of ICSI (<35 years old group: P<0.001; fresh embryo group: P=0.001; frozen-thawed embryo group: P=0.003; cleavage embryo transfer group: P<0.001). Univariate logistic regression analysis showed that the fertilization method in singleton pregnancy had a statistically significant effect on baby SSR ( OR=0.792, 95% CI=0.712-0.881, P<0.001). After removing confounding factors, logistic regression analysis showed that the fertilization method in singleton pregnancy had a statistically significant effect on neonatal SSR (a OR=0.793, 95% CI=0.713-0.883, P<0.001). Conclusion:The fertilization method of assisted reproductive technology can affect the SSR of singleton newborns. The SSR of IVF is significantly higher than that of ICSI and the difference was significant.

Objective:To explore the influencing factors of the secondary sex ratio (SSR) of singleton babies born following assisted reproductive technology.Methods:A total of 7020 single babies delivered by assisted reproductive technology at the Reproductive Medicine Center of the First Affiliated Hospital of USTC (Anhui Provincial Hospital) from January 2000 to December 2018 were collected in a retrospective cohort study. The effect of influencing factors, such as maternal age, fertilization method, embryo transfer type and embryo transfer period on the sex of singleton babies were analyzed.Results:Among 7020 babies, 3730 were boys and 3290 were girls. The total SSR was 113∶100. The SSR of in vitro fertilization (IVF) was significantly higher than that of intracytoplasmic sperm injection (ICSI) fertilization (121∶100 vs. 95∶100, P<0.001), while other factors had no significant effect on the SSR of infants born. In the stratified analysis, there was no difference in SSR between IVF and ICSI in the blastocyst embryo transfer group with mother's age 35 years or older ( P<0.05), while the SSR of IVF in the other groups was higher than that of ICSI (<35 years old group: P<0.001; fresh embryo group: P=0.001; frozen-thawed embryo group: P=0.003; cleavage embryo transfer group: P<0.001). Univariate logistic regression analysis showed that the fertilization method in singleton pregnancy had a statistically significant effect on baby SSR ( OR=0.792, 95% CI=0.712-0.881, P<0.001). After removing confounding factors, logistic regression analysis showed that the fertilization method in singleton pregnancy had a statistically significant effect on neonatal SSR (a OR=0.793, 95% CI=0.713-0.883, P<0.001). Conclusion:The fertilization method of assisted reproductive technology can affect the SSR of singleton newborns. The SSR of IVF is significantly higher than that of ICSI and the difference was significant.