Work

Effects of different seasons on the outcome of in vitro fertilization and embryo transfer: a retrospective cohort study

Year: 2026

Type: article

Abstract: Objective We aimed to investigate the effect of seasons on embryo quality and pregnancy outcomes among infertile patients undergoing in vitro fertilization-embryo transfer (IVF-ET)-assisted pregnancy. Methods We retrospectively analyzed data from 1,413 infertile patients who received IVF and antagonist ovulation induction program in the Reproductive Medicine Center of our hospital from January 2019 to December 2023. Based on seasons, they were divided into the spring group, summer group, autumn group, and winter group. The general information, embryo status, and pregnancy outcome of patients in different groups were compared. Results There were no significant differences in general data, embryo quality, and pregnancy outcomes among the four groups ( P > 0.05). In multivariate binary logistic regression analysis, season did not significantly affect the positive rate of human chorionic gonadotropin (HCG), clinical pregnancy rate, miscarriage rate, and live birth rate. After adjusting beta regression analysis for confounding factors, the blastocyst formation rate in spring was significantly higher than that in summer, the MII oocyte rate in 2019 was significantly higher than that in 2020 and 2022, and the available embryo rate in 2019 was significantly higher than that in 2022 and 2023 ( P < 0.05). Stratified analysis by year showed that in 2020, the blastocyst formation rate in the spring group and autumn group was significantly higher than that in the winter group. In 2022, the HCG positive rate was significantly higher in the spring group than in the summer and autumn groups, and the clinical pregnancy rate was significantly higher in the spring and winter groups than in the summer group. In 2023, the blastocyst formation rate was significantly higher in the spring and winter groups than in the autumn group ( P < 0.05). Conclusion For infertile patients undergoing controlled ovarian stimulation with an antagonist protocol, the rate of blastocyst formation in the spring was higher than that in the summer. There might be a potential interaction between the year and the season.

Source: Frontiers in Reproductive Health

DOI: 10.3389/frph.2026.1782049