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.
For full information about the E-Freeze trial please see the trial Protocol: