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


The latest couple were recruited at Aberdeen Maternity Hospital on 22 April 2017

Total number consented: 607

Why do we need E-Freeze?

Infertility is a common problem and affects approximately one in seven couples in the UK. 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, for the first cycle of fertility treatment, these embryos are replaced 3 to 5 days later. This is called fresh embryo transfer and 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, there is a delay in embryo transfer of between one and three months, allowing the excess hormones of ovarian stimulation to wear off, giving the uterus time to return to its natural state.

Without more research we cannot say if fresh or frozen thawed embryo transfer is better for the first cycle of 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.

Direct link to MP4

General Information

REC Reference:
Clinical Trials Unit:
National Perinatal Epidemiology Unit CTU
University of Aberdeen
NIHR Health Technology Assessment (HTA) Programme
Recruitment Target:
1,086 couples (24 month recruitment period)
Duration of Study:
August 2015 - July 2019