WHAT IS A FROZEN EMBRYO TRANSFER (FET)?
A frozen embryo transfer (FET) is a cycle in which the frozen embryos from a previous fresh IVF or donor egg cycle are thawed and then transferred back into the woman’s uterus.
In 2016, nearly half of all fresh IVF cycles going to transfer at ZEN A.R.T. Fertility resulted in high quality day five or six blastocyst-stage embryos available for freezing. The chance of having embryos available to freeze greatly depends on age. For example, over 60 percent of cycles in which the woman was 35 years old or younger had embryos available to freeze, while less than 20 percent of women over the age of 40 had blastocyst-stage embryos available to freeze.
WHEN CAN I DO AN FET CYCLE?
Frozen embryos remain viable for an infinite amount of time after the initial freeze. You may choose to do an FET cycle following an unsuccessful fresh IVF cycle or after a successful fresh IVF cycle if you’re ready to expand your family.
WHAT ARE THE SUCCESS RATES FOR FROZEN EMBRYO TRANSFERS?
The success rates of an FET cycle are comparable to fresh IVF cycles—and sometimes result in an higher success rate because of the opportunity to optimize the lining of the uterus before implantation, among other reasons. Both fresh and frozen cycles have the same primary indicator for success: the maternal age at the time of embryo freezing. Many patients wait several years between the initial freeze of their embryos and attempting a subsequent FET cycle. Any patient, no matter the amount of time between embryo freezing and thawing, can expect nearly the same potential for success as they experienced with the fresh IVF cycle, which the frozen embryos came from.
Women 35 years and younger have over a 60 percent chance of pregnancy per transfer. This rate declines as the maternal age at the time of the freeze increases.
WHAT ARE THE BENEFITS OF FROZEN EMBRYO TRANSFERS OVER A FRESH (STIMULATED) CYCLE?
In addition to the lower cost, benefits to a FET cycle include:
- Less Medication
Instead of stimulation medication, patients use estrogen and progesterone to thicken the lining of their uterus in preparation for the embryo transfer to allow implantation. Since the stimulation phase was done in a prior cycle, there is also no egg retrieval requiring anesthesia.
- Less Stress
FET cycles are often less stressful than fresh cycles because factors like stimulation response, egg development, and embryo growth were considered during the fresh cycle. Shady Grove Fertility only freezes high quality blastocyst-stage embryos giving patients a significant chance of success with an FET cycle.
Cycles are also more predictable with fewer cycle cancellations. Patients may select the day of their transfer months in advance, which will then be used to determine their cycle initiation date.
WHAT WOULD I EXPECT WHEN STARTING A FROZEN CYCLE?
If you’re ready to proceed with a frozen embryo transfer, contact your local Shady Grove Fertility office and set up an appointment with your physician and nurse to discuss a potential FET cycle. During this time we will review with you your records to ensure the necessary medical testing and screening is current.
At cycle baseline, you’ll be instructed to begin a sequence of about 15 to 22 days of estrogen injections to build the uterine lining. At ‘lining check,’ upon demonstration of a thickened endometrium lining, usually around day five or six, you’ll be instructed to begin progesterone. The morning of the transfer our team of embryologists will thaw the embryo(s) for transfer, a short time later the patient will arrive and the transfer, very similar to what you experience with the fresh cycle, will occur.
Estrogen and progesterone are continued through the blood pregnancy test and is concluded on the 10th week of gestation. The medication helps to continue the thick uterine lining until the placenta can take over.