According to a new study published in Human Reproduction, one of the world's leading reproductive medicine journals, the time of year when eggs are collected from a woman's ovaries during fertility treatment affects fertility rates and IVF outcomes.
Researchers in Australia found that the transfer of frozen and then thawed embryos from eggs collected in the summer resulted in a 30% higher chance of having children 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 total 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.
An improvement in fertility rates was observed regardless of when the transfer of embryos into the uterus took place. Live birth rates at oocyte collection 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 chances of a live birth among women whose eggs were collected on days with the most sunshine compared to days with the least sunshine. The temperature on the day of egg retrieval did not affect the chances of a live birth. However, when transferring embryos 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 clinic in Perth over a period of eight years from January 2013 to December 2021. During this time, 3659 frozen embryo transfers were performed, resulting from 2155 IVF cycles in 1835 patients.
“There are many factors that affect the success of infertility treatment, and age is one of the most important. However, this study puts additional weight on the importance of environmental factors and their impact on egg quality and embryonic development. We have effectively separated conditions during egg collection from conditions during transfer, demonstrating that environmental factors when eggs develop are just as important, if not more so, than environmental factors during implantation and early pregnancy.
< p>Scientists stress that quitting smoking, drinking alcohol and other toxins, and maintaining a healthy level of activity and weight, should be of paramount importance. However, clinicians and patients may also consider external factors such as environmental conditions.
Factors that may play a role in increased 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 it takes three to six months for eggs 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 the miscarriage rate was highest when embryo transfer occurred on the hottest days is consistent with epidemiological studies that show higher miscarriage rates during the summer months.