P-120 Seasonal effects at the time of oocyte collection on the success of frozen embryo transfers

Abstract Study question Does season and duration of daylight hours at the time oocyte collection impact on live birth rates following frozen embryo transfer? Summary answer Frozen transfer in summer had 30% increased odds compared to oocytes collected autumn. What is known already Season conditions fresh or do not appear rates. Recent data from northwest USA suggest summer, independent transfer. design, size, Retrospective cohort study all transfers a single centre Western Australia 2013 - 2021 for which also occurred between these dates. This included 3,659 with embryos generated 2,155 IVF cycles 1,835 patients. Data were analysed by season, temperature recorded sunshine Participants/materials, setting, methods All during period included; demographics, cycle characteristics, embryological clinical outcomes clinic database. Weather Australian Bureau Meteorology. Statistical adjustment was performed factors affect rates, we corrected multiple same patient Main results role chance Compared (FET) retrieval dates autumn, FET (OR: 1.30, 95% CI: 1.04-1.62). Temperature did LBR; there 28% increase when highest tertile lowest day 1.28, 1.06-1.53). These findings remained consistent adjusted respectively. Odds livebirth decreased 18% minimum high low 0.82, 0.69−0.99). The bright appeared drive seasonal variations, whereas ambient associated outcomes. Limitations, reasons caution retrospective study, however populations across seasons, tertiles similar. We analyse subgroups prognosis environmental pollutants this nor assess impacts sperm quality. may results. Wider implications Optimal be retrieval. Consideration could given timing optimise mechanisms remain clarified, though involve melatonin its Trial registration number 2022/ET000980