The time of yr when eggs are collected from women’s ovaries during fertility treatment makes a difference to live birth rates, in response to recent research published today (Thursday) in Human Reproduction, one in every of the world’s leading reproductive medicine journals.

Researchers in Australia have found that transferring frozen then thawed embryos to women’s wombs from eggs collected in the summertime resulted in a 30% higher likelihood of babies born alive, than if the eggs had been retrieved within the autumn.

Dr Sebastian Leathersich, an obstetrician, gynaecologist and Fellow in Reproductive Endocrinology and Infertility at Fertility Specialists of Western Australia, City Fertility Centre, and the King Edward Memorial Hospital in Perth, Australia, who led the study, said: “Over the duration of our study, the typical live birth rate following frozen embryo transfer in Australia was 27 births per 100 people. In our study, the general live birth rate following frozen embryo transfer was 28 births per 100 people. If eggs were collected in autumn, it was 26 births per 100 people, but in the event that they were collected in summer there have been 31 births per 100 people. This improvement in birth rates was seen no matter when the embryos were finally transferred to the ladies’s wombs. The live birth rates when eggs were collected in spring or winter lay between these two figures, and the differences weren’t statistically significant.”

The researchers also found a 28% increase in the probabilities of a live birth amongst women who had eggs collected during days that had probably the most sunshine in comparison with days with the least sunshine.

Until now, there have been conflicting findings on the results of the seasons on pregnancies and live birth rates following egg collection and embryo freezing. Dr Leathersich explained: “It’s long been known that there’s seasonal variation in natural birth rates all over the world, but many aspects could contribute to this including environmental, behavioural and sociological aspects. Most studies IVF success rates have checked out fresh embryo transfers, where the embryo is put back inside every week of the egg being collected. This makes it unattainable to separate the potential impacts of environmental aspects, resembling season and hours of sunshine, on egg development and on embryo implantation and early pregnancy development.

“Lately, many embryos are ‘frozen’ after which transferred at a later date. We realised this gave us a possibility to explore the impact of environment on egg development and on early pregnancy individually by analysing the conditions on the time of egg collection independently from the conditions on the time of embryo transfer.”

Dr Leathersich and his colleagues analysed outcomes from all frozen embryo transfers carried out at a single clinic in Perth over a period of eight years, from January 2013 to December 2021. During this time there have been 3659 frozen embryo transfers with embryos generated from 2155 IVF cycles in 1835 patients. Information on outcomes was missing for 2 frozen embryo transfers and so these were excluded, leaving 3657 for evaluation.

The researchers checked out birth outcomes in response to season, temperatures, and the actual variety of hours of vibrant sunshine (versus calculating hours from sunrise to sunset). They obtained the info on weather from the Australian Bureau of Meteorology. They created three groups for duration of sunshine on days when eggs were collected: low sunshine days (0 to 7.6 hours of sunshine), medium sunshine days (7.7 to 10.6 hours) and high sunshine days (10.7 to 13.3 hours).

“After we looked specifically on the duration of sunshine across the time the eggs were collected, we saw an analogous increase to that seen for egg collection through the summer,” said Dr Leathersich. “The live birth rate following a frozen embryo transfer from an egg that was collected on a day with fewer hours of sunshine was 25.8%; this increased to 30.4% when the embryo got here from an egg that was collected on days with probably the most hours of sunshine. After we took under consideration the season and conditions on the day of the embryo transfer, this improvement was still seen.”

The temperature on the day of egg collection didn’t affect the probabilities of a live birth. Nonetheless, the probabilities of a live birth rate decreased by 18% when the embryos were transferred on the most well liked days (average temperature of 14.5-27.80 C) in comparison with the best days (0.1-9.80 C), and there was a small increase in miscarriage rates, from 5.5% to 7.6%.

Dr Leathersich said: “Our study suggests that the perfect conditions for live births look like related to summer and increased sunshine hours on the day of egg retrieval.

“There are lots of aspects that influence fertility treatment success, age being amongst crucial. Nonetheless, this study adds further weight to the importance of environmental aspects and their influence on egg quality and embryonic development. We effectively separated the conditions on the time of egg collection from the conditions on the time of transfer, demonstrating that environmental aspects when the eggs are developing are as, if no more, essential than environmental aspects during implantation and early pregnancy.

“Optimising aspects resembling avoiding smoking, alcohol and other toxins and maintaining healthy activity levels and weight ought to be paramount. Nonetheless, clinicians and patients could also consider external aspects resembling environmental conditions.”

Aspects that will play a job within the increased live birth rates after egg collection in the summertime and through more sunshine hours include melatonin. Levels of this hormone are frequently higher in winter and spring, and eggs take three to 6 months to develop before they’re released from the ovaries. Differences in lifestyles between winter and summer months may additionally play a job. The finding that miscarriage rates were highest when embryo transfer took place on the most well liked days are consistent with epidemiological studies that show higher rates of miscarriage in the summertime months.

“This implies that the negative effects of hot temperature are more likely related to early pregnancy quite than egg development,” said Dr Leathersich.

Limitations of the study include the undeniable fact that it’s a retrospective quite than prospective study: looking back at what had already happened. For that reason, it cannot show that conditions on the time of egg collection cause the difference in live birth rates, only that they’re related to them.

Dr Leathersich said: “Ideally, these findings ought to be replicated in other sites with different conditions and different treatment protocols to verify the findings. It will even be interesting to have a look at the impact of season and environmental aspects on sperm parameters, as this might have contributed to our observations. We at the moment are planning to investigate this same group of patients using air quality data, as there could also be seasonal changes in exposure to harmful pollutants which could negatively affect reproductive outcomes.

“Finally, given the large increase in so-called “social egg freezing” for fertility preservation and the undeniable fact that this group generally have flexibility about after they decide to undergo treatment, it might be very interesting to see if these observations hold true with frozen eggs which are thawed and fertilised years later. Any improved outcomes on this group could have big impacts for girls making decisions about their future fertility, however the long-term follow up required means it’s more likely to be a while before we are able to draw any conclusions for this population.”

Source:

European Society of Human Reproduction and Embryology

Journal reference:

DOI: 10.1093/humrep/dead137