Embryo Freezing

If you’re considering in vitro fertilization (IVF), you may ask, “What will happen to our extra embryos?” In fact, your embryos (fertilized eggs) can be frozen and then transferred to your uterus, or to another woman’s, years later.

Embryo freezing, called embryo cryopreservation, has helped thousands of infertile couples have healthy babies since the mid-1980s. The process of unthawing frozen embryos and transferring them into a women’s uterus is called frozen embryo transfer (FET).

Who May Consider Frozen Embryo Transfer (FET)?

Candidates for FET are:

• Couples who undergo IVF and have excess embryos they’d like to use later on. They can have a few more chances at pregnancy without having to endure another IVF process involving hormone injections, surgical procedures, numerous doctor’s visits, and emotional and financial tolls.
• Couples in which one partner is undergoing cancer treatment and wants to preserve their fertility for the future. Chemotherapy or radiation treatment that may destroy their ability to produce healthy eggs or sperm.
• Single men and women facing cancer treatment that may render them infertile. They can preserve their sperm or eggs (gametes) and use donor gametes to produce embryos to be used after recovery.
• Infertile couples and single women can use donor embryos to become pregnant.

Most frozen donor embryos come from couples undergoing IVF treatment. For emotional, religious or ethical reasons, some don’t want to destroy (thaw and not use) their excess embryos. Some opt to donate their embryos to infertile couples or for research.

Those donating and receiving embryos must work with a lawyer specializing in third-party reproduction to protect their individual rights and the potential child’s rights.

The Embryo Freezing Process

Embryos can be frozen from one to six days after fertilization. The freezing process involves mixing the embryos with a solution that prevents ice crystals from forming between the cells, which can destroy them. The embryos are then placed in glass vials, which are secured in liquid nitrogen freezers and are cooled slowly to -196° C (-400°F). When needed, the embryos are thawed and bathed in solutions to remove the freezing cryoprotectants.