Frozen embryo transfer (FET) also known as frozen embryo replacement (FER), consists of the thawing of embryos which were frozen during previous IVF or related treatment, and the replacing of them in the uterine cavity at the appropriate time of the menstrual cycle.
It is common during IVF/ICSI treatment for more embryos to be produced than are required at the time. Good quality embryos remaining after the initial embryo transfer can be successfully frozen and stored. It is important to note that about 50% of our patients will have surplus embryos suitable for freezing. The initial maximum duration of storage is 10 years, although this can be extended in certain circumstances. About 85% of embryos survive the freeze/thaw process and maintain their viability. This reduces the need for repeated "fresh" IVF/ICSI cycles with their associated ovarian stimulation and egg retrieval.
The first successful FET cycle was performed in 1983 and many babies have since been born with this technique. No greater risk of abnormalities than that expected from naturally conceived children has been reported. Frozen-thawed embryos may be replaced in a natural cycle (without the use of drugs) or in a cycle controlled by hormonal replacement (HRT cycle).
The replacement (transfer) of frozen embryos can be carried in a "natural" cycle providing the women's menstrual cycle is regular and she is ovulating. In cases where the cycle is irregular or the woman has difficulties coming up to the clinic or she is not ovulating then we prepare the lining of the womb with hormones.
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