Frozen Embryo Transfer

A frozen embryo transfer, or FET cycle, is an IVF treatment cycle using an embryo that was previously frozen and has been thawed on transfer day.  In an ideal IVF cycle, there will be more embryos produced than are initially needed to achieve a pregnancy. When this happens, the extra embryos are frozen (cryopreserved) for future use in an FET (frozen embryo transfer) IVF cycle. Embryos are also cryopreserved when patients choose to do genetic testing via embryo biopsy.

Over the past two years, Carolina Conceptions has done an increasing number of FET cycles. This is mostly because more and more of our patients are choosing to do Preimplantation Genetic Testing (PGS) on their embryos to ensure the embryos are genetically normal with respect to the expected number of chromosomes in each embryo. With PGS, the embryos are biopsied (a few cells are sampled from each embryo) on days 5 and 6 post egg retrieval and are frozen following biopsy. Genetic test results return 7-10 days later. Over the next 3-6 weeks, the mother’s uterus will be prepared for transfer. When she is ready, one healthy embryo(s) is thawed and placed easily into the uterine cavity.

All embryos are cryopreserved with vitrification, an ultra-rapid freezing technique that minimizes the formation of ice crystals in the embryo. High concentrations of a cryoprotectant make this possible. Vitrification is the standard of care for embryo freezing all over the world today and its safety has been proven with no greater risk for fetal anomalies that spontaneous conceptions at home.

Embryos can be frozen for many years and will still result in excellent pregnancy rates. At Carolina Conceptions, 90+ % of embryos survive the thawing process.

In 2019, overall pregnancy rates per FET were 70% with an ongoing pregnancy rate of 65%.