Frozen Embryo Transfer (FET) has become a standard procedure in the In-Vitro-Fertilization (IVF) industry these days. A frozen embryo transfer is a type of IVF treatment where the embryos attained by IVF are cryopreserved (frozen) prior to transfer into a woman’s uterus. The embryos remain safe and stable in the cryopreserved state for weeks to years. The frozen embryos are thawed and transferred to a uterus in the cycle subsequent to the cycle of IVF.  Transfer of cryopreserved embryos has several advantages and it offers higher pregnancy rates and safer pregnancies. When ovaries are stimulated in IVF cycle, they produce multiple eggs for insemination leading to a number of healthy embryos being created. As only one (or two) will be transferred to the uterus immediately, the rest can be frozen for later use. Many centers nowadays recommend routine frozen embryo transfer (also referred to as a “freeze all” approach) where a fresh transfer is not attempted at all. In this case, all embryos are cryopreserved and transferred in a FET cycle in the next month. This is done because the fertility drugs that are used for stimulating the ovaries do not create ideal implantation conditions in the uterus and decreases the pregnancy rate. The more natural environment in the uterus during a later cycle has a better chance of establishing a pregnancy. 

FET is also preferred when

 1) The patient is at the risk of OHSS (ovarian hyperstimulation syndrome) 

2) The endometrial conditions after ovum pick up does not look good on the ultrasound 

3) The hormone progesterone level is high on the day of ovum pick up 

4) Preimplantation genetic testing (PGT) of the embryos is done. 

Freezing embryos is also a potential avenue for women who wants to postpone pregnancy until their late 30s or early 40s and understands that  she may not have suitable eggs of her own by then.