Embryo Cryopreservation is the storage of embryos in sub-zero temperatures. By freezing the embryos and placing them in storage, they can be kept for long periods until they are needed. Embryos are placed in storage at the blastocyst stage. When the patient is ready to conceive the clinical team will make sure the woman is prepared optimally, the embryos are then thawed and transferred into the uterus. Typically, one or two embryos are transferred, and a pregnancy test is performed approximately ten days later to confirm a positive implantation and pregnancy.
FETs, or Frozen Embryo Transfers, can be performed whenever the patient is at the proper stage in her monthly cycle. Doctors will use blood tests, ultrasounds and other tests to determine how long a woman takes to go through her cycle each month. If she has difficulty maintaining a regular cycle, fertility medications may be used to help prepare her for the transfer. Once the doctor has the ovulation cycle regulated and the appropriate time of the month arrives, the embryos are removed from cryogenic storage and thawed carefully to avoid any damage. As soon as the embryos are at the appropriate temperature they can be transferred into the woman's uterus.
FETs are extremely safe, whether a woman uses her own eggs or those of a donor. Donors are thoroughly screened before they are allowed to donate their eggs and sperm. The procedures used to extract the eggs and implant the embryos are also safe for both the mother and fetus, as are the processes used in freezing the eggs, sperm, and embryos. The doctor monitors the health of the mother during the entire process to make sure she can carry a child to term.