Seasonal eggs are collected could make a difference

By Cara Murez HealthDay Reporter

FRIDAY, July 7, 2023 (HealthDay News) — Sunny summer days may improve the chances of successful in vitro fertilization (IVF), according to a new study.

For women undergoing IVF, the season in which her eggs are retrieved could affect embryo transplant success and her chances of delivering a live baby, researchers reported July 5 in the journal human reproduction.

Researchers found that transferring frozen and then thawed embryos into women’s wombs from eggs collected in the summer resulted in a 30% higher likelihood of babies being born alive compared to eggs collected in the fall.

The average live birth rate after frozen embryo transfer was 27 births per 100 people. But if the eggs were collected in the fall, it was 26 births per 100 people. For eggs retrieved in the summer, this was 31 births per 100 people.

“This improvement in birth rates was seen regardless of when the embryos were finally transferred into the wombs of the women,” said Dr Sebastien LeathersichObstetrician, Gynecologist and Researcher in Reproductive Endocrinology and Infertility with Fertility Specialists of Western Australia.

“Live birth rates when eggs were collected in spring or winter fell between these two figures, and the differences were not statistically significant,” he added in a press release.

The researchers also found a link to sunshine, with a 28% increase in the chance of a live birth in women whose eggs were collected on the sunniest days compared to the least sunny days.

“It has long been known that there are seasonal variations in natural birth rates around the world, but many factors could contribute to this, including environmental, behavioral and sociological factors,” Leathersich said.

“Most studies looking at IVF success rates have focused on fresh embryo transfers, where the embryo is put back in place within a week of egg collection. This makes it impossible to separate the impacts potential environmental factors, such as season and hours of sunlight, on egg development and on embryo implantation and early pregnancy development,” he added.

The fact that many embryos are now frozen and transferred later has allowed exploration of the impact of the environment on egg development and on the onset of pregnancy, Leathersich said.

Researchers analyzed the results of all frozen embryo transfers that occurred at a single clinic from January 2013 to December 2021 in Perth, Australia.

Over 3,600 frozen embryos were transferred. They were generated from more than 1,800 patients.

Scientists looked at birth outcomes in terms of season, temperature and number of hours of sunshine, using weather data from the Australian Bureau of Meteorology. The team created three groups for the duration of sunshine on the days the eggs were collected: days with less than 7.6 hours of sunshine; those with 7.7 to 10.6 hours of sunshine; and those with 10.7 to 13.3 hours of sunshine.

“When we looked specifically at the sunshine duration at the time of egg collection, we found a similar increase to that seen for egg collection during the summer,” Leathersich said. “The live birth rate following a frozen embryo transfer from an egg collected on a day with fewer hours of sunlight was 25.8%; this increased to 30.4% when the embryo came from an egg that was collected on days with the most hours of sunlight.

The temperature on the day of egg collection did not affect the chances of live birth, except in certain circumstances. For example, embryos transferred on the hottest days resulted in a live birth rate that decreased by 18%. Miscarriage rates jumped from almost 6% to almost 8% on cooler days.

“There are many factors that influence the success of fertility treatment, 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 egg production. embryonic development,” Leathersich said.

Researchers don’t know why summer and sunshine hours would have a positive impact. They said production of the hormone melatonin is highest in winter and spring, noting that eggs take three to six months to develop before being released from the ovaries.

Seasonal lifestyle differences are another potential reason.

Because the study looked at the conditions rather than recording them as they occurred, it cannot prove a cause and effect relationship. The authors said the results need to be replicated at other sites with different conditions and different treatment protocols.

The US Centers for Disease Control and Prevention has more on successful IVF.

SOURCE: human reproductionpress release, July 5, 2023

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