Frozen Embryo Transfer (FET): Procedure, Risk & Success Rate

by | Jul 26, 2023 | IVF

What is a Frozen Embryo Transfer (FET)?

Frozen Embryo Transfer (FET) is a medical procedure used in In-Vitro Fertilization (IVF) to implant previously frozen embryos into a woman’s uterus. It involves preserving embryos created through in vitro fertilization (IVF) by freezing them at sub-zero temperatures. These embryos can then be thawed and transferred into the woman’s uterus later, in sync with her natural menstrual cycle or a hormonally regulated cycle. This procedure opens up new possibilities, offering hope to couples who have faced challenges in conceiving naturally.


FET Process Step by Step:

Now that we’ve laid the groundwork, it’s time to focus on the magical world of Frozen Embryo Transfer (FET). This unique technique allows preserved embryos to be thawed and transferred to the woman’s uterus at the most opportune time, maximizing the chances of a successful pregnancy.

Step 1: Preparing the Uterine Lining

Before the embryo transfer, the woman’s uterine lining must be adequately prepared to receive the embryo. This typically involves hormonal medications that mimic the natural menstrual cycle, allowing the uterine lining to thicken and become receptive to embryo implantation.

Step 2: Embryo Thawing

The frozen embryos are gently thawed in the laboratory and meticulously cared for to ensure their survival and viability. Thanks to advanced cryopreservation techniques, the vast majority of frozen embryos survive the thawing process, giving immense hope to aspiring parents.

Step 3: Choosing the Best Embryos

Not all embryos have equal potential for implantation and development. Embryologists meticulously assess the viability of thawed embryos, selecting the ones with the highest chances of success for transfer. This careful selection process is crucial in maximizing the odds of a successful pregnancy.

Step 4: Embryo Transfer

The embryo transfer procedure itself is a relatively simple and painless process, akin to a regular gynecological examination. Using a thin catheter, the chosen embryos are gently placed into the woman’s uterus. The number of embryos transferred is often a subject of careful consideration, balancing the desire for a successful pregnancy with the avoidance of multiple pregnancies.

Step 5: The Two-Week Wait

Following the embryo transfer, the woman enters what is often known as the “two-week wait.” During this period, she must patiently wait before taking a pregnancy test. This phase can be both exciting and nerve-wracking, as it holds the promise of life-changing news.

Read to Know: Embryo Freezing (Cryopreservation): Advantages & Succes Rate

Frozen Embryo Transfer Success Rates in India:

According to research and data from renowned fertility centers, the success rates for FET in India vary depending on multiple factors such as the woman’s age, the quality of embryos, and the expertise of the fertility clinic.

For women under 35, the success rates can be as high as 40-50%, while for women over 35, the rates may range from 25-35%. While these numbers may not guarantee a successful pregnancy, they do offer renewed hope for couples who might have lost faith after multiple unsuccessful attempts at conceiving.


Risk of Frozen Embryo Transfer:

  1. Multiple Pregnancies: While FET has brought hope to countless couples, it is essential to address potential risks associated with the procedure. One of the primary concerns is the risk of multiple pregnancies. When multiple embryos are transferred, conceiving twins, triplets, or even more is possible. While this may seem exciting, it can pose health risks to both the mother and the babies.
  2. Pregnancy Loss: Another fear that haunts couples is the risk of pregnancy loss. Despite advancements in reproductive medicine, not all embryos may successfully implant. This can lead to heartbreak and emotional turmoil for couples who have invested their dreams.


Advantages of Frozen Embryo Transfer:

Amidst the risks, frozen embryo transfer offers a myriad of advantages that make it an attractive option for many couples:

  1. Improved Timing and Flexibility: Unlike fresh embryo transfer, FET allows for better timing and flexibility in the cycle, making it more convenient for both the couple and the medical team.
  2. Increased Pregnancy Rates: Studies have shown that FET may yield higher pregnancy rates compared to fresh embryo transfers. The ability to select the healthiest embryos for transfer contributes to this success.
  3. Reduced Cost: FET can be more cost-effective than repeated fresh IVF cycles since it eliminates the need for ovarian stimulation and egg retrieval in subsequent attempts.
  4. Reduced Ovarian Hyperstimulation Syndrome (OHSS) Risk: OHSS is a potential risk associated with ovarian stimulation during IVF. With FET, this risk is minimized or eliminated, making it a safer option for some women.


Fresh vs. Frozen Embryo Transfer:

Frozen Embryo Transfer: Fresh Embryo Transfer involves using embryos created during a current IVF cycle. It allows for immediate transfer after successful fertilization. Picture this: you and your partner have been through the IVF process, and the time has come to witness the culmination of your efforts. The feeling is akin to a marathon runner about to cross the finish line, with nerves and excitement running high.

Frozen Embryo Transfer:  On the other hand, Frozen Embryo Transfer offers the option to freeze and store embryos for future use. This allows for more flexibility in planning and gives your body some time to recover from the intense hormonal stimulation of the fresh cycle. Think of it as a well-deserved rest before continuing the race. The prospect of a frozen embryo transfer might feel like setting sail on a voyage toward a dream, knowing that you have more chances lying ahead.

Read to Know: Who Should do Fertility Preservation & When?

When is the Right Time for Frozen Embryo Transfer?

Timing is the key to a successful Frozen Embryo Transfer. The optimal window for FET is typically around the 19th to 23rd day of your menstrual cycle, also known as the “controlled” or “natural” cycle. During this phase, your endometrial lining is at its prime, creating a nurturing environment for the embryo to snuggle in and flourish.

Imagine preparing a cozy home for a new guest – you want everything to be perfect and ready when they arrive. That’s precisely what you’re doing with your endometrial lining during FET.


What not to eat after embryo transfer?

A: After embryo transfer, it’s advisable to avoid certain foods and substances that could potentially impact implantation or pregnancy. These may include:

  1. Alcohol and Caffeine: Both alcohol and excessive caffeine intake should be avoided during the early stages of pregnancy.
  2. Raw or Undercooked Foods: To prevent foodborne illnesses, avoid raw or undercooked meats, eggs, and fish.
  3. Processed Foods: Opt for a balanced and healthy diet, avoiding excessive consumption of processed or fast foods.
  4. High-Mercury Fish: Limit intake of high-mercury fish like shark, swordfish, king mackerel, and tilefish.
  5. Unpasteurized Dairy: Avoid unpasteurized milk and dairy products due to potentially harmful bacteria.
  6. Smoking and Recreational Drugs: These should be completely avoided during the fertility treatment and pregnancy journey.

Always follow the specific dietary guidelines provided by your healthcare provider for the best possible outcome.


How Long Can Embryos Be Cryopreserved?

Embryos are tiny miracles, delicate yet resilient. Cryopreservation is a scientific marvel that allows us to preserve these precious embryos for an extended period. Under the right conditions, embryos can be safely cryopreserved for years.

Estrogen Levels and Frozen Embryo Transfer:

For a successful FET, your estrogen levels play a crucial role. Too low, and your endometrial lining may not be adequately prepared for embryo implantation. Too high, and it can lead to complications. The sweet spot is different for every individual, but doctors often aim for an estrogen level between 150 and 400 pg/mL.

Finding the perfect estrogen level is akin to fine-tuning a musical instrument – it requires precision and expertise.


HCG Levels After Frozen Embryo Transfer:

After the FET procedure, you enter the nerve-wracking phase of waiting. HCG (human chorionic gonadotropin) is a hormone produced during pregnancy, and its levels can provide crucial insights. Typically, HCG levels double every 48 to 72 hours in early pregnancy.

Waiting for HCG results is like waiting for the plot twist in a captivating novel – you’re eager to know what happens next.

Read to Know: Egg Freezing: Process, Side Effects, Cost and Age Limit


Frozen Embryo Transfer (FET) is a well-established and effective assisted reproductive technology that offers numerous benefits to individuals or couples seeking to build their families. The procedure involves freezing embryos, which can then be thawed and transferred into the uterus during a carefully timed cycle.

FET offers several advantages over fresh embryo transfers, including increased flexibility in timing and reduced risk of certain complications. By undergoing FET, patients can optimize their chances of pregnancy success while minimizing potential health risks.

Though FET boasts high success rates, it is essential to acknowledge that individual outcomes may vary based on factors like age, overall health, and the quality of frozen embryos. Consulting with a fertility specialist can help identify the best course of action for each unique case.



Q: How successful is frozen embryo transfer?

A: Frozen embryo transfer (FET) has shown significant success rates, with many couples achieving successful pregnancies through this method. The success depends on various factors, including the woman’s age, the quality of the frozen embryos, and the overall health of the uterus. While it may not guarantee a 100% success rate, FET has proven to be an effective and viable option for many couples struggling with infertility.

Q: How many days after the period is frozen embryo transfer done?

A: The timing of the frozen embryo transfer is crucial for success. Typically, it is done after the woman’s natural menstrual cycle, around the 14th day after the onset of her period. However, in some cases, hormone medications may be administered to control the timing of the transfer for better synchronization with the uterus lining preparation.

Q: Is frozen IVF better than fresh?

A: The choice between frozen IVF (FET) and fresh IVF depends on individual circumstances. Both have their pros and cons. Some studies suggest that frozen embryo transfer might lead to slightly higher success rates in certain cases, as it allows for better timing and preparation of the uterus. However, each person’s situation is unique, and the decision is best made after consulting with a fertility specialist.

Q: Which embryo is best for transfer?

A: The “best” embryo for transfer is one with high viability and good quality. The embryologists will assess the embryos based on their appearance, growth rate, and overall health. Generally, the embryo that has the highest chance of successful implantation is chosen for transfer. Genetic testing of the embryos (preimplantation genetic testing or PGT) can also provide additional information to select the most viable embryo.

Q: Which day is best for frozen embryo transfer?

A: The optimal day for frozen embryo transfer varies for each individual and is determined based on the woman’s natural menstrual cycle or a hormone-controlled cycle. Typically, the transfer is scheduled around the 14th day after the start of the menstrual period, but it can be adjusted according to the woman’s specific needs and the embryo’s development stage.

Q: What are the disadvantages of frozen embryo transfer?

A: While frozen embryo transfer is a successful fertility treatment, it does have some drawbacks. Some potential disadvantages include the additional cost of freezing and storing embryos, as well as the risk of some embryos not surviving the thawing process. Moreover, the hormonal preparation required for FET can sometimes lead to side effects like bloating or mood swings. However, it’s essential to remember that the advantages often outweigh these drawbacks for many couples.

Q: What happens 7 days after frozen embryo transfer?

A: Around 7 days after the frozen embryo transfer, the embryo should have ideally implanted into the uterus lining. At this stage, some women might experience early pregnancy symptoms like mild cramping or spotting, although it’s essential to remember that these signs are not a guarantee of pregnancy. To confirm the pregnancy, a blood test to measure the hCG hormone levels is usually done about 10-12 days after the transfer.

Q: Can I travel after embryo transfer?

A: It’s generally recommended to avoid long-distance travel immediately after embryo transfer. The two weeks following the transfer are crucial as the embryo needs a stable and nurturing environment for successful implantation. Traveling, especially long flights or journeys, can be physically and emotionally taxing and might disrupt the implantation process. It’s best to discuss travel plans with your fertility specialist and take their advice on the matter.

Q: How do I prepare my uterus for frozen embryo transfer?

A: Preparing the uterus for frozen embryo transfer involves a process called endometrial preparation. This typically includes taking hormone medications like estrogen to thicken the uterine lining and create an ideal environment for embryo implantation. The treatment plan and timing will be tailored to your specific needs, and regular monitoring will be done through ultrasounds and hormone level checks to ensure the uterus is ready for embryo transfer. It’s crucial to follow your fertility specialist’s instructions diligently to maximize the chances of a successful pregnancy.

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    Dr Mona Dahiya

    Dr Mona Dahiya

    IVF Specialist & Consultant

    Dr Mona Dahiya has performed over 5,000+ IVF cycles and is considered a global expert in IVF, ICSI, IUI and male fertility treatment. She is an eminent writer on Infertility Treatment and has over 100 Publications in both International and National Journals. Dr Mona Dahiya has immensely contributed to the field of infertility through her Research and articles.

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