Frozen Embryo Transfer Implantation

Frozen human embryos have now been used for treating infertile couples for many years and have resulted in the birth of several thousand healthy babies. Following thawing, these embryos are replaced in the uterus at the correct time in relation to ovulation and the thickness of the endometrium. The frozen embryo replacement cycle is relatively non-invasive compare to an egg collection cycle. The embryos can be replaced either in a natural cycle or in a hormone-controlled cycle.

In a controlled cycle a gonadtrophin releasing hormone agonist, is first administered to suppress the pituitary gland. Oestrogen tablets, such a Progynova, are administered daily to prepare the endometrium in a spontaneous ovulatory cycle.

The development of the endometrium is monitored by ultrasound scanning; approximately four episodes of scanning will be required, although it can be less. Either when ovulation has occurred, or when the endometrium is thick enough the embryos can be thawed for replacement. The embryos will be thawed so that the developmental stage of the embryos corresponds to the replacement cycle day. The exact timing will depend upon the stage at which the embryos were frozen.

Not all embryos survive the freezing, storage and thawing process. On the morning of the embryo transfer, the embryos are assessed to see if they are suitable for transfer. If they are, then the embryo transfer can proceed. For this procedure a fine catheter is passed through the cervix and the embryos are injected high into the uterus in minute amount of culture medium.

Progestrone preparations, are provided for daily or daily insertion in to vagina from where it is absorbed into the blood circulation to support the endometrium. A pregnancy test is carried out with a blood sample that is withdrawn 12 days after the embryo transfer. The success rate using frozen thawed embryos is between 10 and 30% or more depending on the individual patient’s particular situation and the experience of that IVF unit.