Insemination methods for embryos transferred in frozen-thawed embryo transfer cycles do not impact reproductive outcomes in couples with non-male factor infertility

In couples with of non-male factor infertility, prevailing discussions have focused primarily on patients undergoing fresh embryo transfer. However, whether intracytoplasmic sperm injection (ICSI) improves reproductive outcomes in patients with non-male factor infertility undergoing frozen-thawed embryo transfer (FET) treatment remains unclear. This retrospective study analyzed 57,907 cycles from the Human Fertilisation and Embryology Authority. All FET cycles with non-male factor infertility were initially included. The final included cycles were divided into the ICSI and in vitro fertilization (IVF) groups. Primary outcomes include clinical pregnancy rate, live birth rate, and miscarriage rate; secondary outcomes comprised neonatal outcomes such as birthweight, gestational week, and sex. Binary logistic regression analysis was used to investigate the impact of ICSI on the studied population. The overall clinical pregnancy rate and live birth rate were significantly higher in the ICSI group than in the IVF group (29.6% vs. 26.0%, P < 0.001; 21.5% vs. 19.1%, P < 0.001). However, ICSI showed no significant association with clinical pregnancy or live birth [adjusted OR: 1.01 (0.95, 1.05), P = 0.969; 1.05 (0.86, 1.28), P = 0.611] after adjustment for confounders. Furthermore, while ICSI was associated with increased rates of full-term births and normal birthweight in singletons, these associations were attenuated after adjustment. Finally, ICSI exhibited no significant effect on neonatal sex ratio [adjusted OR: 0.91(0.93, 1.01), P = 0.052]. In conclusion, ICSI was not associated with improved clinical or neonatal outcomes in FET cycles with non-male factor infertility.