A frozen embryo transfer, or FET, is a kind of IVF treatment where a cryopreserved embryo created in a full IVF cycle is thawed and transferred to a woman’s uterus. The cryopreserved embryo may be from a woman’s previous conventional IVF cycle, or it may be a donor embryo. If a donor embryo is being used, the embryo is not genetically related to the woman or her partner.
Frozen embryo transfer or FET is a procedure where embryos that have been frozen or cryopreserved (vitrification) from a previous in-vitro fertilization (IVF) process are transplanted into the uterus/womb of the patient ready to be pregnant.
This procedure is different from the Fresh Embryo Transfer technique. Fresh embryo transfer involves a process where an egg or eggs are taken from the patient during an IVF cycle, fertilized, and monitored for 3 to 5 days to show signs of formation, then placed back in the patient’s womb during the same cycle to gestate.
However, in frozen embryo transfer, an egg or eggs are taken during an IVF cycle, fertilized, and monitored for 5 to 7 days, then are preserved using quality freezing techniques till the patient undergoes another IVF cycle where the embryos are implanted.
FET is a better method of IVF, gaining more popularity with higher success rates compared to the fresh embryo transfer. This is because unlike fresh embryo transfer, frozen embryo transfer gives the hormones time to stabilize, the endometrial lining that has been weakened and thinned from the IVF cycle to recover, and to reduce desynchronization risk
The frozen embryos can be leftover embryos from a previous IVF cycle or can be donated embryos.
TYPES OF FET
When going for a FET procedure, there are two ways to prepare for and achieve the transfer. They include:
In this procedure, immediately after menstruation; mostly after your previous IVF cycle (unless the embryos are donated for much further use), you begin to get administered with hormones for support such as estrogen and progesterone and are monitored to follow your body cycle and make your endometrial lining thicker.
The estrogen always comes first before the progesterone, often 2 weeks before. The embryo transfer then depends on when the progesterone support began and at what stage the embryo was frozen. For instance, if the embryo was frozen on day 3 of observation after retrieval, the embryo will be transferred to the womb on day 4 of the progesterone intake and if it was on day 5 of observation, it would be planted on day 6 of progesterone intake, and so on.
This embryo transfer is done when ovulation occurs naturally without the support of medications. The cycle is monitored closely by your doctors using blood work and ultrasounds as timing is very crucial. You can monitor your ovulation cycle at home using prediction kits, but this may not be as effective as being monitored by your doctor.
Once the right timing or ovulation period is detected, you will be administered progesterone support. The transfer date will depend on the stage of the embryo observation before cryopreservation and when the progesterone supplementation began.
REASONS FOR FROZEN EMBRYO TRANSFER
An embryo transfer can be simply carried out in the same IVF cycle of which the egg or eggs we’re taken, but doctors have found the frozen embryo transfer as a better option and lesser numbers of fresh embryo transfer are recorded.
The reasons for the cryopreservation of embryos before the transfer, which can also be seen as the benefits, include the following:
- It enables enough time for PGT-A or PGT-M, which is a procedure for screening hereditary, genetic, and chromosomal abnormalities.
In a fresh embryo transfer, the designated time for screening is between 3 to 5 days to meet up with the patient’s cycle. But in FET, since the embryo(s) are preserved for future use, further screening can be done within 3 to 7 days. To give more time to study the patient’s ovulation cycle for the perfect timing of an embryo(s) transfer.
In a fresh transfer, the timing may not be favorable in the IVF cycle and the progesterone level may be inadequate. If the transfer is still done, there’s a high risk of failure. FET becomes a better option. The endometrial lining of the womb and the uterus is allowed to return to normal, thicken, and be strengthened. This alleviates the high risk of miscarriage.
Other reasons include:
- The preservation of leftover embryos from a previous IVF cycle for future trials.
- To preserve donated embryos.
BENEFITS OF FET
Compared to fresh embryo transfer, FET has more chances of successful pregnancies with little or no complications. The advantages include:
- Enables more time for the observation and selection of the right timing for an embryo(s) transfer.
- Reduced risks in pregnancies; complications associated with a fresh transfer like preeclampsia, low weight at birth, miscarriages, preterm labor, etc, can be alleviated.
- Reduced risk of ovarian hyperstimulation syndrome (OHSS), a risk commonly associated with fresh embryo transfers.
- Promotes the increased chances of successful and healthy pregnancies, birth, and babies due to the time put into the genetic and chromosomal screening.
- Reduced risk of multiple gestations associated with the conventional IVF procedure, as a single embryo observed to be in a good condition can be selected and transferred.
- All retrieved embryos can be preserved for future use.
- You can choose the gender of your child.
WHO IS ELIGIBLE?
Any woman who is eligible for an IVF cycle is most likely to be eligible for a FET procedure. Also, eligible candidates may include:
- Women with alternating levels of hormones (estrogen, progesterone, etc) and the optimal value of endometrial thickness.
- Women with a previously frozen embryo.
- Women who want their embryo adequately screened for certain genetic traits.
- Women who need an embryo(s) donation.
STAGES (Steps & Procedures)
The frozen embryo transfer is an IVF procedure that takes time and follows through a long line of processes. Starting from the first, its stages include:
The eggs are retrieved from the womb of the patient or donor under an induced ovulation period. Once retrieved, the eggs are inseminated or fertilized (in-vitro) with the sperm of the spouse or a donor and development begins
Based on medical, family, genetic history, etc, the embryos are screened for genetic traits and diseases which can cause abnormalities or risk in pregnancy, birth, and/or the child. This screening takes 3 to 7 days and any abnormality found can be altered.
The screened embryos are vitrified or cryopreserved for when they are needed.
Once you are ready to get pregnant, you will begin medications under monitoring, starting with estrogen drugs on day 2 or 3 of your menstrual cycle. This is to thicken and prepare your endometrial lining. Approximately 2 weeks after close ultrasound monitoring, progesterone medications will be added and a date for transfer fixed.
The transfer date after the first intake of progesterone drugs will be based on the number of days of screening before the embryo was frozen. If the egg was frozen on day 5, the transfer will be done on day 6 of progesterone intake.
A frozen embryo (depending on the number needed by the patient) is taken out and unfroze. This is done on the day of the transfer because it takes a few hours.
After the embryo is thawed, it is ready to be transferred. This procedure is not painless and does not need the patient to be given any form of anesthesia.
It is advisable to have a full bladder, so take a lot of water, between 15 to 30oz between 30 to 60 minutes before the transfer. Make sure to abstain from using any body soap, cream, or perfume as embryos are very sensitive to scents.
Ready for the transfer, the embryo is loaded into a catheter and inserted through the vagina. With the guidance of an ultrasound, it is offloaded into your uterus and the catheter is retrieved. After the procedure, you can rest for a while, go on to empty your bladder, and go back home.
Make sure to come back for follow-up appointments as scheduled by the doctor to keep track of the progress. A blood test called BHCG is often performed to evaluate and control the hormonal value during pregnancy.
TIPS FOR FET
You should know that there are a lot of things and activities that can interfere with the quality and success of FET. So, before the FET procedure, you should keep these in mind:
- Take your medications as prescribed and directed by your doctor.
- Reduce your stress level; take enough bed rest, sleep as much as possible, engage in restive entertainment like reading, listening to music, watching movies, take a stroll, perform yoga, etc, keep your space decluttered, and so on.
- Keep warm; wear warm socks and dress warmly as a cold uterus can be a cause of infertility.
- Keep gadgets that emit high-frequency radiation away from your abdomen and uterus such as phones, laptops, etc. Also, avoid extreme temperatures like hot tubs, sauna, etc, as they can reduce the success rate.
- Avoid any chemicals, especially materials made with endocrine disruptive chemicals (EDCs) and all heavily scented chemicals, to increase the disruption in embryo transfer.
- Eat healthily; avoid cold and highly processed foods. Eat more vegetables, fruits, and healthy fats. Take prenatal vitamins too.
SYMPTOMS & WHAT TO EXPECT AFTER FET
After the embryo transfer, you will have to keep going for follow-up observations and counseling. You should avoid hot temperatures, chemicals, high-frequency radiation as much as possible to increase the chances of your embryo surviving.
Also, there should be no sexual activity during the time until your doctor permits it and this is mostly when the embryo has begun to develop normally to a certain stage. If the transfer is a success, you will be confirmed pregnant after 9 days. Your body will begin to have several changes relating to pregnancy. The fatigue, nausea, the dizzy spells will set in and you will undergo the whole cycle of pregnancy.
Have a lot of bed rest, reduce your stress level, eat healthily, perform easy prenatal exercises, consult with your gynecologist regularly for follow-up tests and ultrasound to see the progress and condition of your baby.
RISKS INVOLVED
The complications of a frozen embryo transfer may include:
- Side effects of fertility or hormonal drugs.
- Cramps, discomfort, and blood spots from the embryo transfer.
- Embryo damage during freezing or thawing.
- Pregnancy complications such as stillbirth, low birth weight, miscarriages, etc, and birth defects. But this risk is way lesser in FET than in fresh embryo transfer.
Compared to fresh embryo transfer, the risk of FET is much lesser and easily controlled. This makes it a more effective and successful procedure.
TIMELINE/CALENDAR
The timeline for a FET procedure from the endometrial preparation to the transfer can take 3 to 4 weeks. The transfer has to be made before the next menstrual cycle begins, so your doctor will work with your periodical calendar. Pregnancy test confirmation can be done after 9 days of the transfer.
SUCCESS RATES
FET has a higher success rate compared to conventional IVF procedures. It has been noted to have an increased level of pregnancies, reduced miscarriages, higher live birth rates, and healthy babies. This success however depends on the age of the patient, the reason for infertility, the quality of the embryos, etc. In recent studies, it has been indicated the women between 20 to 40 years have a success rate of 60%.
COST
The cost of a FET procedure often depends on the following:
- The type of FET you are undergoing; natural or hormone supported.
- The medications are needed for hormone support.
- The observation and monitoring sessions.
- The transfer process, etc.
The average price in the U.S is between $3000 to $6000.
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FAQ
What is the process of freezing an embryo(s) called?
The process is called “vitrification”, a technique that uses a high level of cryoprotectants combined with a rapid cooling rate to freeze the embryos.
What differentiates fresh embryo transfer from frozen embryo transfer?
Fresh embryo transfer is done in the same IVF cycle. The eggs which were retrieved are fertilized and screened for 3 to 5 days and placed back in the uterus within the same cycle. However, in frozen embryo transfer, the eggs are retrieved, fertilized, and screened thoroughly between 5 to 7 days and are frozen for the next IVF cycle or future use.
Why is frozen embryo transfer more recommended than fresh embryo transfer?
Frozen embryo transfer is a more effective way of IVF than fresh embryo transfer. It records a higher success rate, reduces the risk in pregnancy and birth, and birth defects are hardly ever found in babies from FET.
Why does frozen embryo transfer record higher pregnancy rates than fresh embryo transfer?
In frozen embryo transfer, enough time is given for the endometrial lining of the womb/uterus to go back to normal and thicken. A weak endometrial lining can cause complications in pregnancy and may lead to miscarriage. Also, FET gives enough time to monitor and observe the perfect timing for an embryo transfer.
On the other hand, fresh embryo transfer is always done in the same circle leaving very little time for the perfect timing to be determined and for the endometrial lining to recover and thicken from the egg retrieval. Because of this, the embryo transfer may fail or may be miscarried.
Do babies born using FET have a high tendency of being defective?
No, they do not. This is because extra time and attention are giving to screening the embryos for genetic traits that may be defective or abnormal and altering them.
