A frozen embryo transfer (FET) is a procedure where an embryo that was previously frozen during an IVF cycle is thawed and placed into the uterus. It’s one of the most common steps in fertility treatment today, since many IVF cycles produce more embryos than are transferred fresh. Those extra embryos are frozen for future use, and the transfer of one of those embryos into a prepared uterus is what makes up an FET cycle.
How the Full Cycle Works
An FET cycle is not just the transfer itself. It’s a multi-week process of preparing your uterine lining to receive an embryo. From start to finish, a typical medicated FET cycle takes about 6 to 8 weeks.
The cycle often begins with 3 to 4 weeks of daily birth control pills to suppress your natural ovarian cycle and prevent spontaneous ovulation. After that, you’ll have a baseline assessment with bloodwork and an ultrasound. If everything looks good, your doctor will start you on estrogen to build up your uterine lining. After a period on estrogen, you’ll return for another ultrasound and blood draw to check whether your lining has thickened enough. The target is at least 8 millimeters. Research shows that once the lining reaches 8mm, live birth rates are similar whether it measures 10, 13, or even 15mm or more. Below 8mm, pregnancy and live birth rates drop notably.
Once the lining is ready, you begin progesterone, either as daily injections or vaginal suppositories. The transfer is then scheduled for the third to fifth day of progesterone therapy, timed to match the developmental stage of the embryo being transferred.
The Transfer Procedure
On the morning of your transfer, the embryo is thawed at the lab. Modern freezing techniques (called vitrification) give embryos a survival rate of about 97%, a major improvement over older slow-freezing methods, which had survival rates closer to 83%. The vast majority of vitrified embryos look morphologically healthy after thawing, with over 90% retaining all their cells intact.
The transfer itself is quick and usually painless. A thin, flexible plastic catheter is guided gently through your cervix and into your uterus. The embryo is deposited into the uterine cavity along with a tiny amount of fluid. Some doctors use ultrasound guidance during the transfer, in which case you’ll be asked to come with a full bladder. The whole procedure typically takes only a few minutes, and no anesthesia is needed.
Medicated vs. Natural Cycle FET
There are two main approaches to preparing for an FET. In a medicated (also called artificial) cycle, your natural hormones are suppressed and replaced with estrogen and progesterone that you take on a controlled schedule. This gives your doctor precise control over the timing, which makes scheduling easier.
In a natural cycle FET, your body ovulates on its own, and the transfer is timed around your natural hormonal surge. You may need more frequent monitoring with blood tests and ultrasounds so the clinic can pinpoint the right transfer window, but you take fewer medications.
Pregnancy rates are similar between the two approaches. However, a large systematic review published in Human Reproduction Update found that natural cycle FET is associated with a lower risk of adverse pregnancy and newborn complications compared to medicated cycles. Because of this, natural cycle FET is generally preferred for women who ovulate regularly. Medicated cycles remain the standard for women with irregular cycles or those who need more scheduling flexibility.
How Many Embryos Are Transferred
The trend in fertility medicine has moved decisively toward transferring a single embryo. The American Society for Reproductive Medicine recommends that genetically tested (euploid) embryos be transferred one at a time, regardless of the patient’s age. Transferring one tested embryo produces pregnancy rates comparable to transferring two untested embryos, while dramatically cutting the risk of twins and the health complications that come with multiple pregnancies.
For patients under 35 with a favorable prognosis, single embryo transfer is strongly encouraged even without genetic testing. The recommended upper limits increase slightly with age and when embryos haven’t been tested, but for most FET patients working with high-quality frozen blastocysts, one embryo per transfer is the standard.
After the Transfer
You’ll continue taking both estrogen and progesterone after the transfer. A pregnancy blood test is typically done 10 to 12 days later. If the test is positive, you’ll continue the hormones for several more weeks until the placenta takes over hormone production. If the test is negative, you stop the medications and can expect a period within a few days.
Prolonged bed rest after transfer is not recommended and hasn’t been shown to improve outcomes. In the first two weeks, the general guidance is to avoid strenuous exercise, high-impact activities, and core or twisting movements. Walking and light upper body activity are fine. A good rule of thumb is to keep your effort level moderate enough that you can still carry on a conversation while moving. Aim for around 150 minutes of gentle activity per week.
What It Costs
A frozen embryo transfer cycle typically costs between $3,000 and $6,000. This covers the monitoring visits, the transfer procedure, and basic lab work. It does not include the cost of the original IVF cycle, embryo freezing, annual storage fees, genetic testing, or medications, which can add significantly to the total. Insurance coverage for FET varies widely by state and plan, so it’s worth checking your benefits before starting a cycle.