A new study, presented on September 14th at the World Congress of Fertility and Sterility in Munich Germany, suggests that in vitro fertilization rates are significantly higher in the spring (73.5 percent) versus the winter (67.9 percent), summer (68.7 percent) or fall (69 percent).
Scientists have noted seasonal variations in natural conception and birth rates, but now it seems that even artificial insemination may be effected by the seasons. The research team, headed by Dr. Daniela Braga of Sao Paolo, Brazil, studied 1,932 patients undergoing egg retrieval for intracytoplasmic sperm injection – a treatment for sperm-related infertility – at different seasons of the year.
They found no difference in the percentage of developing eggs, high-quality embryos, implantation and pregnancy rates between the winter, spring, summer and autumn groups. Only the fertilization rates varied, but those rates varied a lot. Spring rates are almost one and a half times higher than that of other seasons.
Other experts are not convinced, however. Dr. David Keefe, chairman of obstetrics and gynecology at the NYU Langone Medical Center tells BusinessWeek that he fears that women may be risking their fertility if they wait for times of the year that are supposedly more fertile than others.
“First, when we do in vitro, we’re already overriding the whole system and the hormones that turn on reproduction. And, second, species that have a longer gestation, such as humans, have typically bred when the days are getting shorter, and they (the study authors) found the opposite here,” he says.
“Despite the better results obtained in spring, it is important to highlight that assisted reproduction techniques are effective regardless of the season in which the treatment is being performed,” Braga says.
