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Frozen Embryo Transfer (FET)

What is Frozen Embryo Transfer?

After an IVF cycle, an IVF specialist orders the freezing of some or all of the embryos, depending on the circumstances. Then, the doctor transfers these embryos on specific days of the menstrual cycle after skipping a few cycles. This transfer is known as delayed embryo transfer (Delayed-ET) or frozen embryo transfer (FET), as the process uses frozen embryos. FET, or frozen embryo transfer, helps normalize the exaggerated body response to IVF injections.

Ovarian hyperstimulation syndrome (OHSS) is the top on-list condition where the female body shows an increased reaction to IVF treatment. The patient may feel nausea, vomiting, abdominal pain, and swelling (due to large-sized ovaries). The management includes medical treatment and bed rest for a few weeks so that the body’s hormones reach optimal levels again. After some time, when the patient is ready for transfer, the IVF specialist plans a frozen embryo transfer at a suitable time according to the patient’s preference and her specific menstrual cycle days. 

Embryo Transfer (FET)

Frozen Embryo Transfer Cycle:

The frozen embryo transfer cycle (FET cycle) is the specific and optimal cycle of the female patient when her doctor plans the transfer of her frozen embryos. The usual cycle time is after 1-2 months of IVF cycle. The doctor utilizes this time to treat OHSS (if applicable) or test the genetics of embryos. The doctor selects the frozen embryo transfer cycle for the patient according to the patient’s best health and general feasibility. There are no specific time limitations related to the freezing status of embryos.

The embryologist freezes these embryos in liquid nitrogen at about minus 200C. This low temperature halts all kinds of growth and development in human embryos, enabling the freezing indefinitely. When the patient wants a transfer, the doctor thaws (unfreezes) the embryos, and all the biological growths are resumed. Thus, the embryos are ready for transfer.

What happens during the FET process?

The IVF frozen embryo transfer no longer differs from regular fresh embryo transfer. After selecting the optimal month, the IVF specialist chooses whether to go with a natural cycle transfer or hormonal replacement therapy (HRT) cycle. In the natural cycle, doctors do not prescribe hormonal tablets; they only monitor the uterine lining with ultrasounds. In the HRT cycle, the doctor prescribes hormonal tablets or injections to increase the thickness of the endometrial (uterine) lining. When the endometrial lining reaches a specific thickness ideal for embryo implantation, the doctor carries out the embryo transfer process. The process involves widening the opening of the vagina with an instrument. The doctor injects embryos into the womb near the fallopian tubes (an ideal location for embryo implantation) with the help of a loaded flexible tube called a catheter. This process does not require invasive medical techniques and can be done as outpatient management or may require the patient to stay for a few hours at the clinic. Exceptional circumstances, such as a patient’s desire and a narrowed route, could call for general anesthesia.

When is Frozen Embryo Transfer (FET) Recommended?

IVF experts prefer frozen embryo transfer under the following conditions:

1. For genetic testing:

Genetic testing takes a couple of weeks. Doctors recommend freezing embryos in such cases because they cannot keep them in an incubator for an extended period. Once the embryologist freezes embryos, we have unlimited time to transfer them. The embryologist takes some parts of the embryos (called cells) for genetic testing before freezing. 

2. For the treatment of ovarian hyperstimulation syndrome (OHSS):

Ovarian hyperstimulation syndrome is a condition where the body of the female patient shows exaggerated response to IVF medications. It frequently happens with ladies having a condition called PCOS. PCOS is a hormonal condition that affects women of reproductive ages and has no established specific etiology. Females with PCOS have multiple small-sized cysts in their ovaries. They have many follicles (primarily immature) growing during IVF medications. People with PCOS face infertility, depression, weight gain, pimples,
erratic emotions, hair loss, and unpredictable menstrual periods. Insulin, genetics, and high testosterone are a few possible contributing factors. The patient suffering from OHSS suffers from nausea, vomiting, and abdominal distention. The management of OHSS requires time and close care of the patient.

3. Use of extra embryos in FET:

Sometimes, many good-quality embryos are available for transfer during the fresh cycle. IVF experts advise transferring 1 or 2 high-quality embryos. Embryologists cryopreserve (freeze) the remaining embryos for later use.

4. For Ideal Timing of Transfer:

FET allows greater coordination between the embryo’s developmental phase and its ability to accept the uterine lining. The womb of some patients does not show better acceptability for embryos in fresh cycle transfer. Such cases fall for FET. Ladies with irregular menstrual cycles can significantly benefit from this.

For genetic testing

Doctors recommend freezing embryos in such cases because they cannot keep them in an incubator for an extended period. Once the embryologist freezes embryos, we have unlimited time to transfer them. The embryologist takes some parts of the embryos (called cells) for genetic testing before freezing. 

Use of extra embryos in FET

Sometimes, many good-quality embryos are available for transfer during the fresh cycle. IVF experts advise transferring 1 or 2 high-quality embryos. Embryologists cryopreserve (freeze) the remaining embryos for later use. Females with PCOS have multiple small-sized cysts in their ovaries.

For the treatment of OHSS

Ovarian hyperstimulation syndrome is a condition where the body of the female patient shows exaggerated response to IVF medications. It frequently happens with ladies having a condition called PCOS. PCOS is a hormonal condition that affects women of reproductive ages and has no established specific etiology.

For Ideal Timing of Transfer

FET allows greater coordination between the embryo’s developmental phase and its ability to accept the uterine lining. The womb of some patients does not show better acceptability for embryos in fresh cycle transfer. Such cases fall for FET. Ladies with irregular menstrual cycles can significantly benefit from this.

Fresh vs. Frozen Embryo Transfer:

Fresh and frozen embryo transfers are adaptable options, but there is a general conception that FET is better than fresh cycle transfer. The actual decision relies on specific facts. Based on the situation and the condition of the embryos, a fertility specialist makes choices after considering the couple’s preferences.

A frozen embryo transfer timetable allows the treatment of OHSS. IVF medications might upset the progesterone levels in the human body. Excessively high or low progesterone levels may contraindicate the option of fresh embryo transfer. The hormone takes some time before returning to normal in these situations. An adequate amount of progesterone is essential for a successful pregnancy. FET provides time for PGT, which increases success rates and reduces the danger of transmission of inherited illnesses.

However, there are certain risks associated with frozen embryo transfer. The freezing process may cause limited scale or sometimes massive damage to the embryos. Furthermore, thawing (unfreezing before transfer) may impact the overall survival and quality of the embryo. A fresh embryo transfer is the only practical option for these embryos.

Success Rates of Frozen Embryo Transfer:

According to the research, frozen embryo transfer is a breakthrough, significantly increasing the live birth rate for women with PCOS-related reproductive problems. Another study shows that there is no significant difference in success rates between FET and fresh cycle transfer when treating women with regular periods.

Interestingly, the success rate is less dependent on the type of transfer. Instead, the age of the female emerges as a crucial factor, significantly influencing the production of embryos of varying quality. This finding is of utmost importance for medical professionals and individuals dealing with infertility problems.

Clinical studies of FET:

  1. Research published in the New England Journal of Medicine in 2018 demonstrates that the success rate of FET is greater than the success rate of fresh cycle transfer. It is essential to mention that the population of females used in the study had PCOS, which shows that this success rate is exclusively related to people who are having irregular periods.

  2. According to a 2017 study in PubMed, there is a limited chance that each pickup of oocytes and embryos will result in a healthy pregnancy. Therefore, when choosing the reproductively competent embryo(s) during fresh cycles, cryopreserved extra embryos are less likely to result in a healthy pregnancy. Conversely, if the fresh cycle fails, there’s a greater chance that the embryos will result in a healthy pregnancy after FET.

  3. Another study, published in the British Medical Journal in 2021, did not find any increased rates of live births or continued pregnancies in women utilizing FET. Their population pool had regular menstrual periods (no PCOS). 

Benefits and Risks Associated with FET:

          Benefits of frozen embryo transfer: 

  • The timeline of FET allows for the treatment of OHSS and the testing of embryo genes and gender. 
  • FET is better when surplus embryos are present after an unsuccessful fresh cycle transfer. 
  • FET allows the ideal hormonal balance to maximize the acceptability of the uterus.

    Risks of frozen embryo transfer: 
  • Both the freezing and thawing processes may cause damage to embryos. 
  • Sometimes, the quality of embryos is so low that they are unsuitable for Frozen embryo transfer. Attempting to freeze such embryos may result in their degeneration.

FET and Australian Concept Infertility Medical Center:

The Australian Concept Infertility Medical Center, the leading IVF facility in Pakistan, is committed to providing cutting-edge infertility treatments, including test-tube babies and assisted reproductive technology (ART). With an impressive 26 years of experience in IVF and assisted reproductive techniques, our team of exceptional infertility specialists and professional embryologists, with extensive experience in Pakistan and internationally, are here to help. We offer a comprehensive range of infertility treatments, including IUI (intrauterine insemination), IVF, TIC (timely intercourse), cryopreservation (FET), and PGT (genetic testing). Importantly, our IVF treatments are easily accessible to patients in all major cities in Pakistan.

How do I contact Australian Concept?

First consultations are free of charge at Australian Concept Infertility Medical Center, online or in person. Upon receiving your medical history, an infertility coordinator doctor will schedule any necessary laboratory testing and arrange a consultation with the most suitable infertility specialist. Using the details below, you may make an appointment to see the experts at the Australian Concept Infertility Medical Center in several cities in Pakistan. Schedule a free consultation with us right away. Phone :  (+92)304-1112229 |  Whatsapp :  (+92)309 – 3332229

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