Association between meteorological season and embryo quality in the era of morphokinetics

This study explores the influence of seasonal variations on embryo morphokinetics and the outcomes of intracytoplasmic sperm injection (ICSI) cycles.

This retrospective cohort study, performed in a private university-affiliated IVF center from March 2019 - March 2023, included 1,292 intracytoplasmic sperm injection cycles (ICSI) cycles and 8,376 injected oocytes. Cycles and were split depending on the season in which oocyte collection was performed: Spring (n=462 cycles), Summer (n=176 cycles), Autumn (n=258 cycles), and Winter (n=396 cycles). Embryos were cultured in a time-lapse imaging (TLI) incubation system, and embryo morphokinetics and laboratory and clinical outcomes were compared between the groups.

A slower morphokinetic development was observed in embryos derived from cycles performed in the winter compared to those from cycles performed in other seasons, while embryos derived from cycles performed in the summer exhibited faster embryo development. Significantly longer time to complete synchronous divisions t8-t5 (s3) and second (cc2, t3-t2) and third cell cycles (cc3, t5-t3) were also observed among embryos derived from winter cycles, whereas embryos formed during summer presented shorter cycles. Embryos from cycles performed during summer exhibited a significantly higher KIDScore compared to those from winter cycles. Significantly higher implantation rate was observed in cycles performed in the summer, followed by those performed in the spring.

These findings suggest a potential influence of seasonal factors on embryo development and implantation success. The study underscores the importance of considering seasonal variations and their potential biological impacts on assisted reproductive technologies.