The influence of seasonal variations on in vitro fertilization and fresh/frozen embryo transfer: a retrospective study

To evaluate whether seasonal variations can affect the outcomes of in vitro fertilization (IVF) and embryo transfer (ET).

The data of 2868 IVF-ET cycles over 5 years from patients treated for fallopian tube factors, oligospermia, and asthenospermia were collected retrospectively. The cycles were divided into four seasonal groups based on the day of ET. All cycles were performed using the gonadotropin-releasing hormone agonist and antagonist protocols. The ovarian response, embryo quality, and pregnancy outcomes were compared among groups. In addition, 4106 frozen embryo transfer (FET) cycles performed during the same period were analyzed, and the pregnancy outcomes were compared among the four seasonal groups.

The total dose of gonadotropin in the winter group (2106.04 ± 705.57 IU) was higher than the doses in the spring and summer groups (1994.06 ± 674.95, 2009.07 ± 742.26 IU, P < 0.05). The numbers of total oocytes, matured oocytes, fertilizations, cleavages, and high-quality embryos were comparable among seasonal groups (P > 0.05). Significant differences were not observed among seasonal groups in ET or FET for the implantation rate, clinical pregnancy rate, live birth rate, and miscarriage rate (P > 0.05).

Seasonal variations have little influence on the outcomes of IVF-ET and FET. IVF-ET or FET treatment can be performed during any season.