IVF - In vitro Fertilization

Blastocyst transfers

More evidence is suggesting that patients who have undergone multiple treatment cycles without a successful outcome, having had good quality embryos may benefit from a blastocyst transfer. Women who are at risk of multiple pregnancies may also benefit as one blastocyst is normally transferred.

Blastocyst transfers are normally performed on day 5, rather then day 2 or day 3, following egg collection. The criteria do vary from clinic to clinic but normally four good quality embryos of 8 cells on day 3 following egg collection are required.

Hatching Blastocyst

There are some risks involved by delaying transfer. One of those is that the embryos may not develop to the blastocyst stage. Therefore there may not be an embryo transfer. Blastocyst transfer is allowing the embryos to reach a more mature stage of development and some may not have the potential to do so. They will therefore cease to develop further.

Risks to the children born from blastocyst transfer are still being studied, as it is still a relatively new procedure. However there is evidence to suggest that the chances of identical twins are higher as well as the chances of conceiving a boy.

Freezing of Blastocysts

The freezing of embryos depends on the quality of the embryos. The embryo quality has to be high for them to survive both the freezing and thawing process. Blastocysts have reached a stage of maturity where they are ready to implant therefore clinics offer the freezing of all blastocysts.

The Frozen Embryo Replacement Cycle

Unlike IVF or ICSI a Frozen Embryo replacement cycle does not require the ovaries to be stimulated. Instead Oestrogen is administered, normally in tablet or patch form. This enables the uterine lining to develop for the embryo’s to be replaced. Vaginal scans will also be performed to check that the lining is thickening as result of the Oestrogen theraphy. When the lining has reached approximately 8mm in thickness, the replacement of the embryos will be scheduled. The unit will then advise the woman when to commence Progesterone which will help to maintain the uterine lining. Both Oestrogen and Progesterone are continued until the pregnancy test 14 days after embryo transfer.

Uterine Lining

It is on the day of the embryo replacement that the embryologists will thaw the embryos for the transfer. In some cases, not all of the embryos cryopreserved will thaw successfully.