AFTER THE FERTILITY MEDICATIONS AND OVARIAN STIMULATION, AFTER THE EGG RETRIEVAL PROCESS, AND AFTER FERTILIZATION IN THE LAB, A PATIENT UNDERGOING IVF MAY LEARN THAT THEY HAVE MORE VIABLE EMBRYOS THAN THEY NEED TO TRANSFER IN ONE CYCLE.
A frozen embryo transfer (FET) is a cycle in which the frozen embryos from a previous fresh IVF or donor egg cycle are thawed and then transferred back into the woman’s uterus.
Frozen embryos remain viable for an infinite amount of time after the initial freeze. You may choose to do an FET cycle following an unsuccessful fresh IVF cycle or after a successful fresh IVF cycle if you’re ready to expand your family.
Because you’re not starting a full new IVF cycle, we have to ensure your uterus is ready to accept your embryo. We do this through natural cycle – so monitoring when you are naturally ovulating – and also hormone-controlled, where you’ll be given a drugs protocol specific to you that will make the lining of you uterus grow so that it’s ready to accept your transferred embryo.
In natural cycles we can work out the best date for your transfer using an ovulation predictor kit to check you have ovulated. For hormone controlled cycles you’ll undergo an ultrasound scan at our clinic, where we’ll measure the thickness of the lining to ensure it’s at the optimum level for your embryo. The date of your embryo transfer will be carefully timed according to the development stage at which your embryo was frozen.
Recent studies have provided a great reason for hope when it comes to frozen embryo transfers. Consensus is that in most cases, FET success rates are at least as high as fresh embryo transfer success rates. For some women, FET success rates can actually be much higher than fresh embryo transfers. A study published at Stanford University found that in women over 35 with high progesterone levels, frozen embryo transfers were 73% more likely to result in an ongoing pregnancy than a fresh transfer.
As always, it is needed to keep in mind that each patient is unique, with countless individual factors which can contribute to likelihood of getting pregnant from each embryo transfer, fresh or frozen.
Success rates are not dependent upon the length of time your embryo has been stored. Many families decide to expand their families years down the line. Thanks to the methods and techniques we use to select and freeze embryos, your embryos can remain frozen for many years, with no affect on their quality.
To freeze your embryo we use a state-of-the-art technique called vitrification, or ‘fast-freezing’, which helps to prevent the formation of ice crystals within the embryo. Just before transfer, your embryo is dipped into a special solution called EmbryoGlue, which helps it to ‘stick’ to your uterus.
