The Impact of Seasonal Variation on Clinical Pregnancy and Live Birth Rates in Assisted Reproductive Technology: A Retrospective Cohort Study in Hainan

Objective: To investigate the influence of season on live birth and clinical pregnancy rates, as well as assisted reproductive technology (ART) outcomes, in the Hainan region. Methods: Patients were categorized into four groups based on the dates of artificial insemination and transplantation: spring, summer, autumn, or winter. The main outcome measures were clinical pregnancy rates and live birth rates. Secondary outcomes included body mass index (BMI), oocyte number, two pronuclei (2PN) cleavage rate, total gonadotropin (Gn) dosage and days, age, 2PN fertilization rate, sperm concentration, sperm PR rate, anti-Müllerian hormone (AMH), and endometrial thickness. Outpatient semen quality indicators included sperm PR rate, total sperm count, sperm concentration, and total sperm motility. Results: This retrospective cohort study analyzed 2,016 artificial insemination cycles and 1,783 ovarian retrieval cycles from January 2017 to October 2022, and assessed the semen quality of 6,651 outpatients from May 2017 to October 2022. In artificial insemination cycles, sperm PR rate and clinical pregnancy rate were highest in winter, with a statistically significant difference between groups (P < 0.05). Clinical pregnancy rate was influenced by both age and sperm PR rate (P < 0.05). In ovarian retrieval cycles, the winter group had significantly higher clinical pregnancy, 2PN fertilization, and 2PN cleavage rates than the other groups. The autumn group had higher live birth rates, though not significantly different. Additionally, winter months showed higher total sperm concentration and total sperm number compared to other seasons. Conclusion: Seasonality affected clinical pregnancy and live birth rates in artificial insemination cycles but not in ovarian retrieval cycles in the Hainan region. These findings suggest that while there is no need to choose a specific season for ovarian retrieval cycles, artificial insemination in winter may be preferable for patients.