E-Freeze
Research type
Research Study
Full title
A randomised controlled trial evaluating the clinical and cost-effectiveness of a policy of freezing embryos followed by thawed frozen embryo transfer, compared with a policy of fresh embryo transfer in women undergoing in-vitro fertilization.
IRAS ID
180950
Contact name
Abha Maheshwari
Contact email
Sponsor organisation
Univerity of Aberdeen
ISRCTN Number
ISRCTN 61225414
Duration of Study in the UK
4 years, months, days
Research summary
Summary of Research
1 in 7 couples experience difficulty in conceiving. Many of them will require in-vitro fertilization (IVF) which is recommended by NICE as the effective treatment for infertility. IVF involves hormone injections to stimulate a woman’s ovaries to produce eggs which are removed by a minor operation. The eggs are mixed with sperm to create embryos in the laboratory. These embryos are replaced in the womb a few days after they are created (fresh embryo transfer). Any remaining embryos are frozen such that they can be thawed and transferred at a later date (thawed frozen embryo transfer) for future use. Although this way of providing IVF is still the one which is most widely used, associated pregnancy rates are low (25% live birth rate) and pregnancies resulting from IVF treatment incur an increased risk of complications to mother and baby. These risks appear to be higher after fresh as opposed to thawed frozen embryo transfer.Over the last decade, embryo freezing techniques have improved substantially and recent research suggests that transfer of thawed frozen embryos could lead to higher pregnancy rates as well as fewer complications (both for the mother and the baby) as compared to fresh embryo transfer. An alternative policy which could potentially improve IVF outcomes and reduce complications, therefore, is to avoid fresh embryo transfer, freeze embryos followed by thawing and replacing them at a later date.
However, the existing evidence base is not robust enough to justify such a major change in the way IVF is provided. Hence we propose a large multicentre randomised controlled trial across multiple IVF centres in the UK to evaluate the clinical effectiveness and economic value of a policy of freezing embryos followed by thawed frozen embryo transfer, compared with the current practice of fresh embryo transfer in women undergoing IVF.Summary of Results
In in-vitro fertilisation eggs and sperm are mixed in a laboratory to create embryos. An embryo is replaced within the womb 2-5 days later (fresh embryo transfer), whilst remaining embryos are frozen for future use. Initial research suggested that freezing all embryos and replacing them a few weeks later could improve treatment safety and success. Although this data was promising, it came from small studies was not enough to change practice and policy.
We conducted a large multi-centre clinical study to evaluate the two strategies: fresh embryo transfer versus later transfer of frozen embryo. We also compared the costs incurred for both strategies, during IVF treatment, pregnancy, and delivery.This study was conducted across 18 clinics in 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 later. The study’s aim was to find out which type of embryo transfer gave a higher chance of having a healthy baby.
We found that freezing all embryos followed by frozen embryo transfer did not lead to a higher chance of having a healthy baby. There were no differences between groups in live birth, miscarriage rates and pregnancy complications. Fresh embryo transfer was less costly from both a healthcare and patient perspective.
A routine strategy of freezing all embryos is not justified, given no increase in success rates but extra costs and delays to embryo transfer.REC name
North of Scotland Research Ethics Committee 1
REC reference
15/NS/0114
Date of REC Opinion
3 Nov 2015
REC opinion
Favourable Opinion