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The E-Freeze trial results have now been published

View full results


E-Freeze is a multi-centre randomised controlled trial that compares fresh embryo transfer with frozen thawed embryo transfer for couples undergoing their first, second or third round of fertility treatment. The main aim of E-Freeze is to understand if there is any difference in the chance of having a healthy baby.


Total: 619

Recruitment to the E-Freeze trial is closed.
We would like to thank all the couples and site staff who took part.

Why do we need E-Freeze?

Despite improvements in technology, IVF success rates remain low with an overall live birth rate of 25% per treatment.

IVF uses hormone injections to stimulate a woman's ovaries to produce eggs, which are then removed and mixed with sperm to create embryos. Normally, fresh embryo transfer is used, where the embryos are replaced 3 to 5 days later. Any remaining embryos are usually frozen, so that they can be used at a later date if required – a process known as thawed frozen embryo transfer.

There have been some small studies, which suggest that using frozen thawed embryos may lead to improved pregnancy rates. This is because when frozen embryos are used, this allows time for the excess hormones of ovarian stimulation to wear off and for the uterus to return to its natural state.

Without more research we cannot say if fresh or frozen thawed embryo transfer is better for fertility treatment. E-Freeze will compare these two types of embryo transfer in 1,086 couples from IVF centres throughout the UK to find out which, if any, gives the best chance of having a healthy baby.

Trial Information

EudraCT No.:
REC Reference:
Clinical Trials Unit:
National Perinatal Epidemiology Unit CTU
University of Aberdeen
NIHR Health Technology Assessment (HTA) Programme
Recruitment Target:
1,086 couples
Duration of Study:
August 2015 - July 2019
Logo: Human Fertilisation and Embryology Authority
Fertility Network UK

Updated: Monday, 25 September 2023 12:35 (v55)