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expert reaction to study on the time of year of egg collection and number of babies born via IVF

A study published in Human Reproduction looks at season at the time of oocyte collection and frozen embryo transfer outcomes.


Dr Ying Cheong, Professor of Reproductive Medicine, University of Southampton and Director of Complete Fertility, said:

“Leathersich et al is a retrospective study in western Australia on over 3600 frozen embryos transfers over a 8 year period, and they reported that those embryos created from eggs collected in the summer months have a 30% increase in live birth compared to those created during autumn.

“Seasonal variations are known to be associated with clinical outcomes, such as what we have already experienced with Covid-19. But I doubt the seasons alone can cause these variations; other biological, procedural and human factors associated with seasons are likely in play. For example, there were over 300 less procedures in the summer compared to the winter, and workload is known to influence productivity and efficacy even in clinical care.   

“Such associative data is useful and interesting, but I would not recommend that patients rush in only for summer treatments. Fertility treatment requires significant amount of careful planning, and patients must only come for their fertility treatment when they are clinically and psychologically ready, and not only when the sun shines.”


Prof Alastair Sutcliffe, Professor of General Paediatrics, University College London (UCL), said:

“While the press release is a good reflection of the work, the work itself is pretty speculative and there is no accounting for confounders. It is an established fact that of those who freeze their oocytes very few women return for them and there are much more powerful factors relevant to conception such as BMI, Age and Non Smoking which need to be addressed. This speculative research needs to be put in the context of those. I would say there are close to zero implications in the real world. One would also expect from this work that there are higher conception rates in sunnier countries and this is not the case.”



‘Season at the time of oocyte collection and frozen embryo transfer outcomes’ by S.J. Leathersich et al. was published in Human Reproduction at 00:05 UK time on Thursday 6 July.




Declared interests

Dr Ying Cheong: “Director of Complete Fertility.”

Prof Alastair Sutcliffe: “No conflict of interest with this study.”

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