FET (Frozen Embryo Transfer)

    Last updated date: 13-Mar-2023

    Originally Written in English

    FET (Frozen Embryo Transfer)

    FET (Frozen Embryo Transfer)

    Presently, every clinic's IVF program must include freezing. Research has shown that embryo transfers performed later in unstimulated cycles rather than immediately after egg collection yield superior results. Clinics all across the US and the rest of the globe are moving toward freezing all embryos and transferring them later after the female partner's body has recovered from stimulation. This is due to improved freezing techniques. This method entails freezing every embryo during an IVF cycle and transferring them one at a time after thawing in subsequent, unstimulated cycles. By minimizing multiple pregnancies, which raise the health risks for both the mother and the unborn baby, the total live birth rates per IVF attempt are maximized.




    In an IVF procedure known as a frozen embryo transfer (FET), a cryopreserved embryo made during an earlier egg retrieval cycle is thawed and transferred to the uterus. FET frequently makes use of frozen embryos that the gestational parent already owns from a prior traditional IVF procedure. Donor embryos may also be cryopreserved embryos. Donor embryos can be utilized in a variety of ways during FET. Full embryo donation, egg donation that can be inseminated with partner sperm and subsequently frozen, and sperm donation that can be inseminated into partner egg donation and then frozen are available options.


    Frozen vs Fresh Embryo Transfer

    Frozen vs Fresh Embryo Transfer

    Although it isn't always best, a fresh embryo can be advantageous in some circumstances. For older patients who have embryos that may have a better chance in utero without awaiting genetic tests, or for younger patients without a suspected chromosomal abnormality, fresh embryos may be advised (occasionally embryos used in genetic testing have to be frozen).

    According to research, the success rates of fresh and frozen embryos are quite similar. Fresh embryos may have a slight advantage, according to certain research, although the benefit is typically small. Additionally, some research indicates that using frozen embryos in specific circumstances results in a marginally higher cumulative live birth rate.

    When a fresh transfer is not tried, some clinicians advise elective frozen embryo transfer, commonly known as a freeze-all approach. All of the embryos in this scenario are cryopreserved and transferred in a FET cycle within the upcoming month. Embryos can be safely stored and preserved for use in the future through cryopreservation.


    Why Choose Frozen Embryo Transfer?

    Frozen Embryo Transfer

    Your doctor might recommend FET to help you get pregnant if you have particular medical issues, relevant circumstances, or lifestyle considerations.


    You Have Extra Embryos

    IVF can produce one or more embryos, but only one or two can be safely transferred at once. High-order multiple pregnancy risk is increased by the transfer of several embryos. If you have a good prognosis, your doctor might advise an elective single embryo transfer (eSET) to lower this risk. Regardless of the outcome of this transfer, you can still have extra embryos after the cycle. After your IVF cycle, you might decide to freeze or cryopreserve any extra embryos to give yourself more choices in the future. Let's imagine you get five embryos and your physician suggests an elective single embryo transfer for you (one embryo will be used and the four others will be cryopreserved). You have a few options if the transferred embryo doesn't lead to a successful pregnancy. These consist of performing an additional new, complete IVF cycle or transferring one or two of your earlier cryopreserved embryos. The most inexpensive option is frequently to transplant one of your already frozen embryos.


    You Want Another Child

    If your fresh embryo transfer led to your previous pregnancy and you later decide you want to give your IVF-conceived kid a sibling, you might still have embryos in cryopreservation. Embryos that have been cryopreserved can last a lifetime.


    You are Using Genetic Screening

    Both preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS), which are assisted reproductive technologies, examine embryos for particular genetic disorders or flaws. On the third or fifth post-fertilization day, following egg retrieval, a biopsy is used to do this. Occasionally, the outcomes of genetic screening and testing are available in time for a fresh embryo transfer. The embryos that were biopsied will all be cryopreserved, nevertheless, if a day five biopsy is performed if the genetic testing is complex and takes additional time. Your doctor can choose which embryos to transfer for a FET-IVF cycle after the test results are in.


    You Choose an Elective Procedure

    The finest reproductive medications for ovulation stimulation may not always result in the most favorable uterine conditions for implantation, according to some researchers' views. This may imply that using a frozen embryo after that is more likely to produce a viable, healthy pregnancy than a fresh transfer. Three to five days following egg retrieval, all embryos are cryopreserved using the freeze-all procedure. A frozen embryo transfer can happen the following month or in the month after, after the endometrium has had time to grow without the help of ovarian-stimulating medications. Your doctor might recommend hormonal drugs to improve endometrial receptivity during that FET round (especially if you do not ovulate spontaneously). Your doctor might perform the FET using a hormonal medication-assisted natural cycle.


    You are at High Risk of OHSS

    Ovarian hyperstimulation syndrome (OHSS) is a potential side effect of fertility medications that, in severe and uncommon circumstances, can result in infertility and even death. Before a fresh embryo transfer, it might be postponed if your risk of OHSS seems high. All of the embryos will then be cryopreserved. It could be necessary to cancel because pregnancy can make OHSS worse. If you're pregnant, it can also take longer for you to recover from OHSS. An embryo transfer cycle using frozen embryos might be planned once you have healed from OHSS.


    Your Fresh Embryo Transfer Was Canceled

    There may be further causes for canceling a fresh embryo transfer. For instance, if you contract the flu or another illness after egg retrieval but before the transfer, you might not be able to undergo FET. Additionally, if the ultrasound results for the endometrial conditions are not favorable, your doctor can advise cryopreserving all of the embryos before arranging FET-IVF for a later time.


    You are Using an Embryo Donor

    Some couples decide to give their extra embryos to another couple that is having trouble becoming pregnant. Your cycle will be a frozen embryo transfer if you want to use an embryo donor.


    Which Approach is Best?

    fresh embryo transfer

    According to certain research, frozen embryo transfers result in slightly higher pregnancy rates than fresh embryo transfers. According to additional studies, pregnancies that are conceived following a frozen embryo transfer may have better results.

    The majority of research, meanwhile, has been conducted on healthier, younger women. It is therefore uncertain what outcomes people beyond the age of 35 or with a bad prognosis could anticipate.

    It is necessary to conduct more high-quality research to ascertain whether FET-IVF is more likely to result in live childbirth than a fresh transfer and, if so, why. Additionally, individual aspects related to your particular medical diagnosis may influence which approach is most appropriate for you.

    Another thing to think about is the possibility that embryos that make it through cryopreservation are stronger than those that don't. Weaker embryos may be less likely to endure prolonged storage and the freeze-thaw cycle. Frozen embryo transfer entails a risk; however, some medical professionals believe that a viable pregnancy wouldn't have resulted from the weaker embryos.

    Older studies evaluated frozen vs fresh transfers and came to the conclusion that fresh transfers resulted in higher pregnancy rates. That study, however, cannot be used with a freeze-all cycle. It makes sense that the less-than-ideal embryos would have poorer success rates than the good-looking ones that were transferred in a fresh cycle since the previous research involved extracting the less-than-ideal embryos, freezing them, and then promptly transferring the best-looking ones.


    Frozen Embryo Transfer Procedure

    Hormone support cycles and natural cycles are the two types of FET-IVF cycles. The most popular FET-IVF cycle is a hormonally-supported cycle, which appeals to a lot of people, clinics, and labs due to the controllability of the transfer day and the availability of hormonal support for any ovulatory issues. You must be informed of what is achievable with each FET-IVF type if you want the procedure to be done by your primary physician or on a particular date. The day when progesterone starts can be adjusted for a synthetic cycle, but it's unpredictable for a natural cycle.


    FET With Hormonal Support

    FET With Hormonal Support

    Similar to a standard IVF cycle, a FET-IVF cycle with hormonal support begins at the end of the prior menstrual cycle. You will receive injections of a substance designed to regulate and stop the reproductive cycle. This treatment is typically the GnRH agonist Lupron, but it can also occasionally be another pituitary-suppressing agent.

    Your clinic will do a baseline ultrasound and bloodwork once you start your period. You will start taking estrogen supplements if everything looks good. This will ensure the endometrial lining's health. After around two weeks of this, you will have another ultrasound and additional blood testing. You will add the hormone progesterone after about two weeks of estrogen therapy. You might require vaginal suppositories or progesterone injections in oil.

    The timing of the embryo transfer is determined by the stage at which the embryo was cryopreserved and the beginning of progesterone supplementation. If the embryo was cryopreserved, for instance, on day five after the egg was recovered, the frozen embryo transfer would take place six days after progesterone supplementation began. A FET-IVF cycle has the advantage of requiring considerably less monitoring than a standard IVF cycle.


    FET Natural Cycle

    FET Natural Cycle

    A FET natural cycle bases the timing of the embryo transfer on the natural timing of ovulation. The embryo transfer's timing must be precise. It needs to take place a specific number of days following ovulation. That day will vary depending on whether the embryo was frozen on day 3 or day 5 post-egg extraction, as with a hormone-supported cycle.

    The cycle is closely monitored because timing is so important, either at home with ovulation prediction tests or at the doctor's office with ultrasounds and blood tests. Most doctors use ultrasound and blood tests to time the transfer because ovulation predictor kits aren't always simple to interpret. The clinic plans your transfer date when ovulation is confirmed, and you start taking progesterone supplements.

    According to certain research, natural cycles have an advantage over hormone-supported cycles. The research is still in its early stages and is not yet conclusive. The most effective endometrial priming protocol is still up for discussion, according to the authors of thorough analysis on the subject published in 2021. Additionally, the researchers note that it's almost certain that there are individual differences that favor one approach over another.


    Timeline for Frozen Embryo Transfer

    1. Planning a FET cycle. Notify your doctor as soon as you decide to start a freezing cycle by getting in touch with his office. After that, he will check your records to make sure your pre-screening is updated.
    2. Preparing the lining of your uterus. A FET cycle will last 6 to 8 weeks. A cycle normally starts with an injection of Leuprorelin to suppress the regular ovarian cycle on around day 21 of your cycle.
    3. Transferring the embryo. The embryo transfer is a quick process that takes only a few minutes to finish. Neither anesthesia nor recovery time is required. The transfer is arranged by your nurse.
    4. The pregnancy test. You'll test for pregnancy two weeks following the embryo transfer.


    Frozen Embryo Transfer Risks

    Frozen Embryo Transfer Risks

    The dangers of a frozen embryo transfer cycle are much lower than those of a full IVF cycle. Ovarian hyperstimulation syndrome (OHSS) is one of the main dangers of IVF and fertility medications. Ovarian stimulating medications are not used in a FET cycle, hence OHSS is not a problem.

    Many embryos will withstand the freeze and thaw process with cryopreservation. It is possible to re-biopsy an embryo if the results of the PGT test are inconclusive (it is not obvious if the embryo is normal or not). This slightly but considerably lowers the success rate.

    Risks associated with embryo transfer include an increased chance of ectopic pregnancy and a very minor chance of infection. The possibility of having multiple pregnancy may also increase (which comes with its own set of dangers for pregnant women and the fetuses they are carrying) depending on how many embryos are transferred.

    Embryos that have been frozen, thawed, and then re-biopsied, as well as those that have been refrozen, run the danger of being lost or having a decreased success rate when it comes time to thaw them for use. However, this does not imply that a fresh transfer is always the best option.

    According to some studies, there is a chance that children born through frozen embryo transfers will be large for gestational age. However, a meta-analysis revealed that transfers of frozen embryos may result in healthier pregnancies and offspring than transfers of fresh embryos. Babies born via frozen embryo transfer had a lower risk of preterm birth, stillbirth, and low birth weight, according to a study's findings.

    Another study evaluated the chances of birth defects in offspring from fresh IVF procedures, frozen embryo transfers, and spontaneous conceptions. In comparison to children born spontaneously, the study indicated that birth abnormalities were three times more likely to occur with fresh IVF transfers. However, the transfer of frozen embryos did not show this increased risk (perhaps because these frozen embryos could have been evaluated with PGT). Overall, there was still a very minimal risk of birth abnormalities.


    Frozen Embryo Transfer Cost

    Frozen Embryo Transfer Cost

    If you ask your doctor how much FET will cost, make sure they give you a complete price because there can be additional costs for the procedure. You can plan your budget accordingly with the use of this information. A frozen embryo transfer typically costs between $3,000 and $6,500.

    The costs related to the actual transfer procedure as well as monitoring and hormonal assistance are included in the average price. Natural cycles are slightly less expensive because they don't include fertility medications. However, the price does not include the costs of the initial IVF procedure, the initial cryopreservation of the embryos, or any storage fees.



    While it might seem natural to prefer using fresh embryos for IVF over frozen ones, this is frequently not the case. Many IVF patients find that frozen embryo transfer is a suitable option that is on par with or superior to using fresh embryos. Numerous unique criteria will determine whether or not FET is right for you. The best person to ask about whether or not this method is right for you is your doctor.