Embryo freezing is a very important tool for couples undergoing IVF. In most of the patients, either a single embryo transfer or maximum of two embryos are transferred in the cycle in which IVF is being done. Multiple embryo transfer is avoided to avoid the risk of multiple pregnancies whichmay be hazardous to the mother or the growing foetuses. After the embryo transfer, whatever number of good embryos are left are frozen using the vitrification method.
Frozen Embryo Transfer can be done in the immediate cycle if the pregnancy fails to happen. In those patients who have a successful outcome, the embryos can be frozen for a long time and can be used for the second pregnancy. This gives the advantage of doing the embryo transfer more than once with only one egg retrieval cycle. The quality of embryos when thawed usually remains the same as at the time of freezing but in a few cases all embryos retrieved may not be of the same quality. Embryos can be frozen any time between Day 2 to Day 5.