This study was designed to investigate the influence of seasonal variations on the number of retrieved ova, fertilization rate, embryo quality rates and pregnancy rate in IVF cycles. Prospective cohort study was conducted on a total number of 2140 cycles in infertile patients undergoing their first IVF cycle between 2000 and 2007 in IVF policlinic. Chi2-test, Pearson's correlation coefficient and one-way analysis of variance were used for statistical analyses. Overall fertilization rate was 77.96% and pregnancy rate 29.15 +/- 2.72% per cycle. Seasonal prevalence of pregnancy rate was highest during fall 33.8 +/- 4.5% and lowest during summer 23.4 +/- 6.2%, but these differences did not reach statistical significance. The study did not show any statistically significant differences in the number of retrieved oocyte, fertilization, and embryo quality according to season. Therefore seasonal changes should not be taken into account in everyday IVF practice.
Kirshenbaum, M., Ben-David, A., Zilberberg, E., Elkan-Miller, T., Haas, J., & Orvieto, R. (2018). Influence of seasonal variation on in vitro fertilization success. PLoS ONE, 13(7). https://doi.org/10.1371/journal.pone.0199210