The study was carried out by the University of Western Australia and Fertility Specialists of Western Australia. It followed 84 women who underwent a total of 140 IVF cycles.
The difference between this and the other studies that we have covered is that the women had all previously undergone IVF cycles where the embryo had failed to implant in their womb. This is called Recurrent Implantation Failure and affects around 10% of couples.
Here the researchers split the women into two groups. One group received a fresh embryo transfer and the other group received a frozen embryo transfer.
They then looked at fresh v frozen embryo success rates and found that the fresh embryo group had pregnancy rates of 27.1% and live birth rates of 20.8%. The frozen embryo group had pregnancy rates of 45.1% and live birth rates of 39.2%.
There is clearly a substantial difference here. Why is it that frozen embryos appear to be so much better? The leader of the study, Professor Roger Hart, believes that the reason relates to the different timings used in fresh and frozen cycles.
In a typical fresh IVF cycle women receive various hormones to stimulate their ovaries to produce eggs. This is effective at encouraging eggs to develop but can lead to excessive amounts of hormones in a woman’s body which may negatively affect their wombs and result in an unnatural environment for implantation.
With frozen embryos on the other hand transfers take place some time after stimulation and this time gap gives a woman’s body time to return to a more natural state.
Professor Hart concludes:
“One of the things to draw from this study is that some women should opt for a frozen embryo transfer over a fresh IVF cycle, which may help improve the implantation potential of the embryo.”
If you have suffered implantation failure using fresh embryos in the past you may want to consult with your doctor to see if using frozen embryos would be appropriate for you.
The study was published in the Australian and New Zealand Journal of Obstetrics and Gynaecology and is available here (The interval transfer of a frozen‐thawed embryo is more successful than a fresh embryo transfer for women undergoing IVF with recurrent implantation failure after cleavage stage embryo biopsy. Aust N Z J Obstet Gynaecol March 2018).