Understanding Frozen Embryo Transfer (FET)

After the retrieval and fertilization phases of an in vitro fertilization (IVF) cycle have been completed, there are several options for how the ensuing embryos are implanted into a woman’s uterus. One of these methods is a frozen embryo transfer (FET). In FET, embryos are cryopreserved through a process known as vitrification, which is a rapid-freezing method that uses cryoprotectants and cryogenic technology to transmute embryos into a glass-like, stable state. FET can be useful in a wide range of scenarios.

FET and Having a Surplus of Eggs
In IVF, egg retrieval is accomplished through a process known as ovarian stimulation, in which hormonal medications are used to trigger egg production and maturation as well as boost the production of estrogen. To increase the odds of a successful pregnancy and birth, the IVF retrieval process typically harvests several eggs. While the number of eggs retrieved is dependent on how well the ovaries respond to stimulation, the average number of eggs retrieved ranges from 8 to 15.

After the eggs are retrieved, they are combined with sperm, either in a petri dish with a culture medium or through intracytoplasmic sperm injection (ICSI), a process in which a single sperm is injected directly into an egg. If fertilization is successful, this process will produce multiple viable embryos that can be implanted into the woman’s uterus.

However, although there may be multiple embryos available, the American Society for Reproductive Medicine (ASRM) often recommends that patients undergoing IVF opt for elective single-embryo transfer (eSET) instead of having multiple embryos implanted all at once. eSET helps prevent multiple pregnancies, which are risky for both the mother and the fetuses. Multiple pregnancies also often lead to premature births, which not only can cause immediate complications but also can lead to long-term health problems, such as cerebral palsy.

Patients who have a surplus of high-quality embryos have the option of freezing their embryos for possible future implantation. Through FET, they can have an additional child later without having to go through a full IVF cycle all over again.

FET and Preimplantation Genetic Testing
FET is also utilized in preimplantation genetic testing (PGT), which refers to a set of diagnostic procedures that examine embryos for genetic anomalies or chromosomal abnormalities. In PGT, the outer layer of the embryos is biopsied for analysis. While the tests are performed, the embryos are frozen to keep them stable and viable. If the tests come back showing that the embryos are healthy, the embryos can be thawed and implanted into the woman’s uterus.

Reproductive Issues and FET
In some cases, transferring a frozen embryo is a better choice after IVF than having a fresh embryo implanted. These situations include patients with:

• Uterine lining issues
• A history of failed implantation or miscarriage in previous IVF cycles
• Polycystic ovarian syndrome (PCOS)

Learn More
As a form of assisted reproduction, FET helps expand your IVF options for implantation. To learn more, contact Chelsea Fertility NYC today.