The E-Freeze trial shows no evidence to suggest that freezing embryos and then transferring at a later date leads to a higher chance of having a healthy baby than fresh embryo transfer

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Published on Friday, 10 June 2022

The main E-Freeze trial results have now been published in journal of Human Reproduction. The NIHR HTA Final report is also available here.

The trial was conducted in 18 clinics across the United Kingdom from 2016-2019, 619 couples participated. Couples were allocated to either having an immediate fresh embryo transfer or freezing all embryos and having a transfer at a later date. The trial's aim was to find out which of these two types of embryo transfer gave a higher chance of having a healthy baby.

The original target had been to recruit 1,086 couples, however the trial was stopped early due to lower than expected recruitment rates and a greater than expected number of couples switching from their allocated group of frozen embryo transfer to fresh embryo transfer.

The E-Freeze trial found no evidence to suggest that freezing all embryos followed by embryo transfer at a later date leads to a higher chance of having a healthy baby. There were also no differences between groups in live birth, miscarriage rates and pregnancy complications.

Results from E-Freeze therefore do not lend support to a policy of routine freezing for everyone, given that there was no evidence to suggest improved success rates but there are additional costs and delays associated with frozen embryo transfer.

A summary of the results are also available in the E-Freeze results podcast and infographic.

For more publications from E-Freeze, including the Protocol and Statistical Analysis Plan Publication please visit the E-Freeze website.

E-FREEZE was funded by the National Institute for Health and Care Research (NIHR).The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.