Research

Why frozen embryo transfer?

Frozen embryo transfer breaks the link between ovarian stimulation and embryo transfer, giving time for the uterus to return to its natural state

The idea for E-Freeze originally came about from some small research studies that showed that the pregnancy rates seemed to be higher for frozen embryo transfer than fresh embryo transfer.

The research suggested that there may be a benefit to freezing embryos. For an embryo to grow it needs the right conditions in the uterus. Using frozen embryos, breaks the link that currently exists between ovarian stimulation and embryo transfer. When embryos are frozen, there is a short break in treatment, often 4 to 6 weeks and the uterus has a chance to return to its natural state.

Whilst the research was suggestive of a benefit without, more research we cannot say which type of embryo transfer is better. E-Freeze is a large trial being conducted across the UK, with 1086 couples. It will help us to understand whether fresh or frozen embryo transfer is better for pregnancy rates and live birth rates or whether there is no difference at all

For details of the research that led to the E-Freeze trial please see the research articles below:

Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfer in normal responders.

Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfers in high responders.

Since the E-Freeze trial launched there has been further research into the comparison of fresh embryo transfer with frozen embryo transfer. Research, published last year, into infertile women suffering with polycystic ovary syndrome, found that frozen embryo transfer was associated with a higher live birth rate:

Fresh versus Frozen Embryos for Infertility in the Polycystic Ovary Syndrome.

Global Research

Thinking big. E-Freeze is leading a global collaboration of fertility studies that will further understanding of IVF. Map of the world showing participating regions or countries. They are: Australia, China, Denmark, Hong Kong, Netherlands, United Kingdom, the USA and Vietnam.

E-Freeze is not just about the research being done in the UK. E-Freeze is leading a global research collaboration with 7 other studies around the world. The research being done now will help to inform the fertility treatment of the future.

This study is funded by the National Institute for Health Research (NIHR) Health Technology Assessment (HTA) Programme (Reference Number 13/115/82). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

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