You may undergo a frozen embryo transfer (FET) cycle whenever you have frozen embryos and wish to use them. This may be after the delivery of a child when you wish to come back and use your frozen embryos to grow your family, or it could be after an unsuccessful stimulated in vitro fertilization (IVF) cycle in which you had embryos cryopreserved.
Note: You must undergo a fresh stimulated IVF or donor egg cycle first, in order to have embryos to freeze.
What To Expect
Unlike a fresh stimulated IVF cycle, an FET cycle requires very little testing in advance. You need to have current (within the last year) infectious disease bloodwork. Additionally, if you are returning after a delivery or certain types of gynecological surgery, your physician may require an updated mock embryo transfer (MET) and a hysterosalpingogram (HSG), if indicated. You can easily complete this testing once the cycle start dates have been established and you have started on the cycle/month of oral contraceptives (birth control pills). You and your partner will need to update your informed consents for FET cycles every 6 months. Both partners must sign.
THE FET PROCESS
When you decide to begin a frozen cycle, please contact our office and let us know. We will then review your records to ensure your pre-screening is up to date. If necessary, we will order any repeat screening tests. If appreciable time has passed since you last consulted with your physician, we will schedule a follow-up visit with your physician.
A FET cycle will take approximately 6 to 8 weeks. A cycle typically begins with 3 to 4 weeks of daily birth control pills to suppress the normal ovarian cycle, as it would lead to ovulation. After the course of birth control, you will need a baseline assessment involving bloodwork and ultrasound. Depending on the test results, your physician may instruct you to begin sequential injections of estrogen to build the uterine lining. After a designated period of time on the estrogen injections, you will return for bloodwork and a transvaginal ultrasound lining check. If the lining check demonstrates that your hormone levels are appropriate and your endometrial lining has thickened, your physician will likely instruct you to add daily injections or vaginal suppositories of progesterone to your medication regimen. Your nurse will then confirm an FET date and you will come in for your transfer several days later. Estrogen and progesterone continue after the transfer, and through the blood pregnancy test about 2 weeks later.
What are the benefits of an FET cycle over a fresh stimulated cycle?
FET is often a good choice over a fresh stimulated cycle if you have frozen embryos to use. Benefits include:
Less complex treatment
Fewer monitoring appointments
No risk of ovarian hyperstimulation syndrome (OHSS)
No anesthesia or egg retrieval
Significantly reduced medication cost
Nearly identical success rates
What kind of fertility medications will I take when doing an FET cycle?
You will need supplemental estrogen and progesterone medications to prepare your uterine lining for the FET. You will also continue these medications after the FET. Estrogen is often given in the form of injections on every third day. You may also need progesterone injections or vaginal suppositories every day as instructed after the lining sonogram check. If you are unable to tolerate injectable medications, you can discuss with your physician alternative forms of these medications.
How do frozen embryos allow physicians to perform genetic testing?
If you have a risk of passing certain genetic conditions on to your children, we can test the embryos for certain genetic mutations. This is called preimplantation genetic diagnosis (PGD). After the physician retrieves the eggs and they are fertilized, the embryologist will biopsy each suitable embryo. The embryologist will then freeze the embryos while awaiting results from the biopsied cells. The physician can then transfer only embryo(s) for which testing indicates the genetic mutation (and corresponding medical condition) in question is absent.
In addition to testing for genetic mutations (PGD), embryo freezing has allowed for preimplantation genetic screening (PGS). This screening looks for abnormalities in chromosome number, such as trisomy 21, which causes Down syndrome, and many others that are likely to result in implantation failure or miscarriage. Likely candidates for this testing include patients with failed implantation and older women, who are at higher risk for chromosomal abnormalities.