What is the Origin of Frozen Embryo Transfer?

The term is a descriptive clinical phrase combining "frozen," referring to the cryopreservation process, with "embryo transfer," the final step of placing the embryo into the uterine cavity. The development of reliable cryopreservation techniques, initially slow-freezing and later vitrification, in the late 20th century revolutionized IVF. This innovation allowed for the safe storage of surplus embryos, decoupling the hormonal stresses of ovarian stimulation from the critical implantation window.

What is the Mechanism of Frozen Embryo Transfer?

The success of FET hinges on meticulously preparing the recipient's endometrium to mimic the natural window of implantation. This preparation typically involves exogenous administration of estrogen to thicken the endometrial lining, followed by progesterone to induce the necessary secretory changes. Once the lining reaches the appropriate thickness and hormonal phase, the thawed embryo is gently transferred into the uterus, where it is hoped to implant and initiate a viable pregnancy.

Frozen Embryo Transfer

Meaning

Frozen Embryo Transfer (FET) is a core procedure within assisted reproductive technology (ART) where an embryo, previously cryopreserved after an in vitro fertilization (IVF) cycle, is thawed and subsequently placed into a prepared recipient uterus. This technique offers significant clinical advantages, including the ability to perform preimplantation genetic testing and to optimize the hormonal environment of the recipient woman in a cycle separate from ovarian stimulation. FET has substantially improved cumulative pregnancy rates per egg retrieval cycle.