Seasonal Influences on Different Stages of In Vitro Fertilization: Stimulation and Fertilization


1 Biostatistics Department, Tarbiat Modares University ,Tehran, Iran

2 Anatomy Department, Tarbiat Modares University, Tehran, Iran


Effect of seasonal changes in human reproduction has been intensively researched. Some studies acknowledge influences of seasonal variation on natural conception, while others can not confirm them. The aim of this study was to investigate the effect of seasonal changes on different stages of assisted reproductive technology (ART) in Tehran.

Materials and methods
This study was carried out on 268 cycles which were the first intracytoplasmic sperm injection (ICSI) cycle of the couples between July 2005 and March 2007. Multiple logistic regression was used to model the influence of different clinical factors on pregnancy rate and a bivariate Poisson regression model was used for modeling the number of mature oocytes and obtained embryos.

Based on the logistic regression model, the duration of infertility, female age, number of mature oocytes, and transferred embryos were only the significant predictors. In this series, seasonal changes had no predictive value on the pregnancy rate. Bivariate Poisson regression model showed that only the female age and duration of infertility were the factors simultaneously affecting the number of embryos and mature oocytes.

The suspected seasonal variability on the outcome of ICSI cycles has not been confirmed. Furthermore, among different seasons, there are no significant differences in the number of mature oocytes, obtained embryos, and transferred embryos.