Anyone undergoing IVF treatment may be slightly better off getting their eggs harvested in summer, according to a new study by Australian researchers.
Embryos harvested in summer were 30 per cent more likely to result in a live birth than those collected in autumn, according to the peer-reviewed study that was published in medical journal Human Reproduction on Thursday.
"Over the duration of our study, the average live birth rate following frozen embryo transfer in Australia was 27 births per 100 people," lead researcher Dr Sebastian Leathersich said.
"In our study, the overall 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 if they were collected in summer there were 31 births per 100 people."
Leathersich said the birth rates for spring and winter lay between the two outlying figures and "were not statistically significant".
The study also found a 28 per cent increase in the chances of a live birth when eggs were harvested on days with the most sunshine compared to those with the least.
"When we looked specifically at the duration of sunshine around the time the eggs were collected, we saw 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 that was collected on a day with fewer hours of sunshine was 25.8 per cent; this increased to 30.4 per cent when the embryo came from an egg that was collected on days with the most hours of sunshine.
"When we took into account the season and conditions on the day of the embryo transfer, this improvement was still seen."
The study analysed 3657 frozen embryo transfers made at a Perth clinic between 2013 and 2021.
Leathersich said that, by examining frozen eggs rather than fresh transfers, he and his team were able to isolate the impact of environmental factors like sunshine in the success of an IVF birth.
"It's long been known that there is seasonal variation in natural birth rates around the world, but many factors could contribute to this including environmental, behavioural and sociological factors," he said.
"Most studies looking at IVF success rates have looked at fresh embryo transfers, where the embryo is put back within a week of the egg being collected.
"These days, many embryos are 'frozen' and then transferred at a later date.
"We realised this gave us an opportunity to explore the impact of environment on egg development and on early pregnancy separately by analysing the conditions at the time of egg collection independently from the conditions at the time of embryo transfer."
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Because the study was retrospective, Leathersich said further research was warranted.
"Ideally, these findings should be replicated in other sites with different conditions and different treatment protocols to confirm the findings," he said.
"It would also be interesting to look at the impact of season and environmental factors on sperm parameters, as this could have contributed to our observations."
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