The time of year that eggs are collected from women's ovaries during fertility treatment affects fertility rates and IVF outcomes, according to a new study published in the journal Human Reproduction, one of the world's leading journals in reproductive medicine.
Researchers in Australia found that transferring frozen-then-thawed embryos from eggs collected in the summer resulted in a 30% greater chance of children being born alive than if the eggs were retrieved in the fall.
According to a retrospective cohort study, The average live birth rate after frozen embryo transfer was 27 births per 100 people. In the current study, the overall fertility rate after frozen embryo transfer was 28 births per 100 people: if the eggs were collected in the fall, then 26 births per 100 people, but if they were collected in the summer, then 31 births per 100 people.
Improvements in fertility rates were observed regardless of when the embryos were transferred to the uterus. Live birth rates for oocyte collections in spring or winter were between these two figures, and the differences were not statistically significant.
The scientists also found a 28 percent increase in the odds of a live birth among women whose eggs were collected on days with the most sunlight, compared to days with the least amount of sunlight. Temperature on the day of egg retrieval did not affect the chances of a live birth. However, when embryos were transferred on the hottest days, the chances of a live birth were reduced by 18% compared to transfers on the coolest days, and there was also a slight increase in the miscarriage rate from 5.5% to 7.6%.
Dr Lezersich and colleagues analyzed the results of all frozen embryo transfers performed at one Perth clinic over an eight-year period, from January 2013 to December 2021. During this time, 3659 frozen embryo transfers were performed from 2155 IVF cycles in 1835 patients.
“There are many factors that influence the success of fertility treatment, and age is one of the most important. However, this study adds further weight to the importance of environmental factors and their influence on egg quality and embryo development. We have effectively separated conditions during egg collection from conditions during transfer, demonstrating that environmental factors while eggs are developing are as important, if not more important, than environmental factors during implantation and early pregnancy.
< p>Scientists emphasize that avoiding smoking, drinking alcohol and other toxins, and maintaining healthy activity levels and weight should be of utmost importance. However, clinicians and patients may also consider external factors, such as environmental conditions.
Factors that may play a role in increasing the number of live births after oocyte collection in the summer and during periods of more sunshine include melatonin. Levels of this hormone are usually higher in winter and spring, and eggs take three to six months to develop before they are released from the ovaries. Differences in lifestyle between the winter and summer months may also play a role. The finding that miscarriage rates were highest when embryo transfers occurred on the hottest days is consistent with epidemiological studies that show higher miscarriage rates during the summer months.