IVF Frozen Embryo Transfer (FET)

Patients may choose IVF FET due to various conditions or circumstances.

You Have Frozen Embryos After a Fresh IVF Transfer Fails – During IVF treatment, one or several embryos may result. It is only safe, however, to transfer one or a couple at a time. Transferring multiple embryos increases the risk of a high-order multiple pregnancy (like triplets or quadruplets.) In fact, to further reduce this risk, some doctors recommend “elective” single embryo transfer in patients with a good prognosis.

Sometimes, there are “extra” embryos after an IVF cycle. Most people choose to freeze or cryopreserve their extra embryos. For example, let’s say you get five embryos. Let’s also say your doctor recommends elective single embryo transfer for you. This would mean that one embryo will be transferred, and the four others will be cryopreserved.

Let’s say that one embryo transferred doesn’t result in a successful pregnancy. In this case, you have two options: You can do another fresh, full IVF cycle, or you can transfer one or two of your previously cryopreserved embryos. The most cost-effective option would be to transfer one of your previously frozen embryos. This also cuts down the amount of drugs and treatment you need to have to achieve pregnancy and this is the option many couples decide to go with.

2. You Want to Give Your IVF-Conceived Child a Sibling – If your fresh embryo transfer resulted in pregnancy, you may have embryos still waiting in cryopreservation. Cryopreserved embryos can remain on ice indefinitely so if in the future, you decide to do a FET-IVF cycle to give your child a sibling, you can. Your other option would be to do another fresh cycle and not use your cryopreserved embryos.

3. Fresh Embryo Transfer Canceled – OHSS or Ovarian Hyperstimulation Syndrome is the most common reason for a fresh embryo transfer to be canceled, but there are other possibilities. Your fresh transfer may need to be canceled if you get the flu or another illness after egg retrieval but before transfer. Also, if the endometrial conditions don’t look good on the ultrasound, your doctor may recommend freezing all embryos. At a later date, you can schedule a FET-IVF.

4. You’re Using an Embryo Donor – Some couples choose to donate their unused embryos to another infertile couple. If you decide to use an embryo donor, your cycle will be a frozen embryo transfer.

What Can You Expect?

1. First, your specialist will decide on a protocol. In some cases, there is a clear reason for choosing one protocol over another. Other cases rely on a review of many factors, including cause of infertility, clinician and patient preference, and response to previous protocols. In other words, it’s very complicated and half the time it’s either hard to know what is best in advance, or it will make little difference to your chances of success either way.

At the basic end, you have the natural FET. You are monitored for ovulation and thickness in your lining, and embryo transfer is scheduled for several days after ovulation. The exact timing will depend on the age of the embryos at transfer. If you have frozen the embryos at day two, transfer will happen two days after ovulation. If you have frozen the embryos at day five, transfer will happen five days after ovulation, and so on. The idea is to mimic the natural process as closely as possible. As in the natural situation, the timing doesn’t have to be ultra-precise, with studies showing there is up to twenty-four hours leeway.
A natural cycle may be used with or without some form of luteal phase support. Commonly you will be given two or three hCG injections and/or progesterone supplements (pessary-style or injections). Again, protocols for luteal phase support vary wildly, sometimes starting before transfer, sometimes the day of transfer, some continuing until beta (and perhaps beyond if your test is positive), and others continuing only for a set number of days, no matter what.

If you don’t ovulate reliably on your own, your specialist may use an ovulation induction (OI) protocol, in which ovulation of a single follicle is induced (usually using FSH injections). You will either be monitored for a natural LH surge, or triggered with an hCG injection. Transfer and luteal phase support happens as per a natural protocol.

Hormone replacement therapy (HRT) protocols are favoured by some specialists, and for some patients. These use hormone tablets, patches, pessaries or injections to mimic the natural cycle, plus or minus a GnRH agonist/antagonist to shut off your body’s natural control. The simplest and most common protocol seems to be oestrogen tablets until the lining is thick and ready, followed by progesterone supplements, with transfer happening near the beginning of the “luteal” (progesterone) phase.

2. Prior to transfer, your embryo will be thawed out. 58% of embryos survive the thaw. By thawing the day before transfer, the lab ensures plenty of time to thaw extra embryos if need be. It also gives a chance to see if the embryo will resume growth after thawing – those that don’t are very unlikely to survive inside the uterus.

It’s also possible to thaw a batch of embryos and grow them for a few days prior to transfer–for example, if you have decided to grow day two embryos to blast. An embryo can be thawed, grown, and re-thawed providing it remains of good enough quality.

3. The transfer itself is exactly like a fresh transfer. The procedure is similar to an IUI (which feels a bit like a pap smear) except it is performed in the hospital for easy access to the laboratory where embryos are kept and thawed, instead of in the doctor’s rooms. You are usually given a short period of rest, and your doctor will let you know if there are any other instructions. Some doctors prefer you to rest for a day or more, just on the off-chance this helps, although numerous studies show no benefit to restricting your normal activities for more than twenty minutes after the transfer is done.

Problems That May Arise And Ways To Handle Them:

A frozen embryo transfer cycle has significantly fewer risks than a full IVF cycle. One of the primary risks to IVF (and fertility drugs) is ovarian hyperstimulation syndrome (OHSS). However, you don’t need to worry about OHSS in a FET cycle since ovarian stimulating drugs aren’t used.

1. Depending on how many embryos are transferred, there is a risk of multiple pregnancy. Even twin pregnancies come with an increased risk to the mother and babies. Embryo transfer comes with a slightly increased risk of ectopic pregnancy.

2. With cryopreservation, some embryos may not survive the freeze and thaw process. With elective frozen embryo transfer, this means you may lose embryos that would have been available if you had done a fresh transfer.

3. Cysts and other growths. If a cyst is discovered at the beginning of your cycle, your doctor may want to treat it before going ahead with transfer.

4. Ovulation is not happening or the lining is not thickening. Most of the time, your specialist will simply prescribe extra drugs and continue monitoring. If the problem is severe, your cycle may be cancelled and a new protocol put in place for next time.
5. It’s a natural cycle and ovulation is missed. Your cycle will be cancelled and you will be monitored more closely next time, or placed onto a medicated cycle for greater control.

6. Embryos do not survive the thaw. From personal experience, it is possible to thaw four embryos, one by one, in the twenty-four hours prior to transfer, and almost certainly more, depending on how quickly each succumbs. This is, of course, wrenching in its own way, but as long as there are embryos left, you will not need to worry about your cycle being cancelled.

If none of your embryos survive the thaw, it’s possible to start a full cycle straight away. For example, if you usually start sniffing or around day 21 or so of the cycle prior to EPU, you can start your drugs within a week of your cancelled transfer day.

7. Unusual spotting in the middle of your cycle. If it’s happening in your luteal phase, your specialist may prescribe extra drugs to support the lining. If it happens prior to transfer, your cycle may be cancelled pending investigation – depending on the opinion of your specialist. Unusual spotting is very common, not always explainable or treatable, and can happen even in successful cycles. Having said that, please report it to your doctor immediately.

A frozen embryo transfer is easier, physically and emotionally, than a full cycle. As you can see, problems do sometimes arise, but most people find things go fairly smoothly until beta day – so please try not to let the above list panic you! There is often some trial and error involved in finding the best protocol for your body. Good luck – and yes, FETs do work for many people!

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