Collecting eggs during the right season may impact IVF success.

Collecting eggs during the right season may impact IVF success.

The Impact of Summer and Sunshine on IVF Success Rates


Sunny summer days may be more than just an enjoyable time to spend at the beach; they may also increase the chances of successful in vitro fertilization (IVF), according to a recent study. This research suggests that the season in which a woman’s eggs are retrieved can affect the success of embryo transplantation and her likelihood of delivering a live baby. The study, published in the journal Human Reproduction, found that transferring frozen then thawed embryos to women’s wombs from eggs collected in the summer resulted in a 30% higher likelihood of babies born alive compared to eggs collected in the fall.

Dr. Sebastian Leathersich, an obstetrician, gynecologist, and fellow in reproductive endocrinology and infertility at Fertility Specialists of Western Australia, explains, “This improvement in birth rates was seen regardless of when the embryos were finally transferred to the women’s wombs.” The live birth rates for eggs collected in spring or winter fell between the rates for summer and fall, but the differences were not statistically significant.

One interesting finding from the study was the link between sunshine and IVF success rates. As the researchers discovered, there was a 28% increase in the chances of a live birth among women who had eggs collected during days with the most sunshine, compared to those with the least sunshine. This correlation between sunshine and IVF success rates adds another layer of complexity to the already multifactorial process of fertility treatment.

It has long been recognized that there is seasonal variation in natural birth rates worldwide, but the specific factors contributing to this variation remain uncertain. Previous studies on IVF success rates primarily focused on fresh embryo transfers, making it difficult to separate the potential impacts of environmental factors, such as season and hours of sunshine, on egg development and early pregnancy development.

However, with the growing prevalence of freezing embryos for later transfer, researchers now have an opportunity to explore the impact of the environment on egg development and early pregnancy. For this study, the researchers analyzed outcomes from over 3,600 frozen embryo transfers that took place at a single clinic in Perth, Australia, between January 2013 and December 2021.

The scientists examined birth outcomes in terms of season, temperature, and the number of hours of bright sunshine. They found that the duration of sunshine around the time the eggs were collected had a similar impact on birth rates as the overall season. The live birth rate following a frozen embryo transfer from an egg collected on a day with fewer hours of sunshine was 25.8%. In contrast, this rate increased to 30.4% when the embryo came from an egg collected on days with the most hours of sunshine.

While temperature on the day of egg collection did not significantly affect the chances of a live birth, certain circumstances showed exceptions. Embryos transferred on the hottest days had a decreased live birth rate by 18%, while miscarriage rates increased from nearly 6% to almost 8% on the coolest days.

The study’s lead researcher, Dr. Leathersich, commented, “There are many factors that influence fertility treatment success, with age being among the most important. However, this study adds further weight to the importance of environmental factors and their influence on egg quality and embryonic development.”

It is worth noting that the study cannot establish a cause-and-effect relationship because it relies on retrospective analysis rather than real-time data recording. The authors recommend further replication of the findings in different locations with varying conditions and treatment protocols.

The exact reasons why summer and sunshine may have a positive impact on IVF success rates remain uncertain. One hypothesis points to the hormone melatonin, which is more abundant in winter and spring. It takes three to six months for eggs to develop fully before they are released from the ovaries, suggesting a potential role of seasonal hormone fluctuations. Additionally, seasonal lifestyle differences may also contribute to the observed variations.

In conclusion, this study sheds light on the impact of environmental factors, specifically summer and sunshine, on the success rates of IVF. The findings highlight the importance of considering external factors when analyzing fertility treatment outcomes and may provide valuable insights for both patients and healthcare providers. However, further research is necessary to fully understand the underlying mechanisms and validate the results in diverse settings.

More information The U.S. Centers for Disease Control and Prevention has more on successful IVF.