Couples who turn to embryo transfer in their quest for parenthood should understand the differences between fresh and frozen embryo transfer.
Fresh embryo transfer is a procedure where fertilized eggs – embryos – are transferred to the uterus of the intended mother several days after the egg retrieval. The eggs may have been harvested from the woman’s ovaries or may come from an egg donor. To ensure there are a number of quality eggs for retrieval, the ovaries are stimulated using fertility drugs. The harvested eggs are then fertilized in the lab using sperm from the male partner or a sperm donor.
When a woman undergoes ovarian stimulation, estrogen levels climb, and progesterone is produced once the final maturation of the eggs is triggered. The embryo transfer must be carefully timed to ensure proper synchronization between the endometrium (i.e., uterine lining) and the embryo. On day five following fertilization, one or two of the best quality embryos are transferred to the uterus. Any remaining embryos may be frozen for later use.
Frozen embryo transfer, also known as FET, involves the use of embryos that have been previously frozen. These embryos may have been cryopreserved following a previous IVF cycle or may be frozen donor embryos. In some cases, these embryos represent the remaining embryos following a previous IVF cycle with a fresh embryo transfer. In other cases, all embryos are frozen following an IVF cycle, and no fresh transfer is performed. For all women/couples undergoing preimplantation genetic screening (PGS) to determine the chromosome status of the embryos, those embryos must be frozen to allow for the testing results to be obtained. A normal embryo is then transferred during a subsequent FET cycle.
In the past, fresh embryo transfer was considered superior to frozen embryo transfer, but many studies have shown that results for the two are at least similar. In some cases, frozen embryo transfer may be safer.
A study published January 11, 2018, in the New England Journal of Medicine revealed IVF with the transfer of frozen embryos in women with infertility associated with polycystic ovary syndrome resulted in a higher live birth rate than fresh embryo transfer.
Studies have also shown women who opt for frozen embryo transfer have a lower risk of ovarian hyperstimulation syndrome (a condition where hormone medication causes the ovaries to become swollen and painful) than those who undergo fresh embryo transfer. Women who achieve pregnancy following a frozen embryo transfer also have a lower risk of preterm delivery compared to those who conceive following a fresh IVF cycle. Freezing also allows time for embryos to undergo genetic screening or testing prior to being frozen.
Not every embryo survives freezing and thawing but with improved cryopreservation techniques now available, the vast majority of high-quality embryos do survive. Since frozen embryos can remain in storage indefinitely, they may be transferred at any time. Some women choose to undergo fresh embryo transfer with the first cycle of IVF and preserve remaining embryos for later transfer. In this case, her chance of pregnancy when she ultimately uses the frozen embryos is determined by the age at which the embryos were created, not her age when she decides to do a FET cycle.
While medication and treatment costs may be lower when using frozen embryos, there is additional cost involved for the freezing and thawing process as well as ongoing storage.
Both fresh and frozen embryo transfer can result in pregnancy and live birth. Each option has advantages and disadvantages, and couples should consider all options to determine which best fits their needs.
Contact your local URA clinic in Hasbrouck Heights, Hoboken, and Wayne, NJ for more information. Your friendly URA team will be happy to determine which transfer method would work best for you and provide more details.
