Preparing for Frozen Embryo Transfer (FET): Do’s and Don’ts Explained by an Expert

Frozen Embryo Transfer (FET) has become a prevalent practice in assisted reproduction, offering various benefits over fresh embryo transfers. There are numerous reasons why embryos may be frozen before transfer, with genetic testing being the most common. The flexibility that FETs provide in preparing the endometrium (the lining of the uterus) is invaluable in ensuring the optimal timing for embryo implantation. In this article, we will explore how to prepare for FET, the procedures involved, and the important do’s and don’ts to ensure the best chances of success.

Dr. Francisco Anaya, Gynecologist from the UR Vistahermosa shares with us some important insights into the preparation of the frozen embryo transfer and its do’s and don’ts.

Preparing for Frozen Embryo Transfer

“Nowadays, in Assisted Reproduction, we perform more and more Frozen Embryo Transfers (FETs). Many causes can lead to deferring embryo transfer, but the most frequent is the carrying out of genetic testing on the embryos.

“The cycles with Frozen Embryo Transfers also allow us to have more flexibility with the endometrial preparation. These cycles with the transfer of vitrified embryos allow a little more flexibility in the endometrial preparation, aimed at finding the optimal moment of endometrial receptivity (also called implantation window) for embryo implantation to take place”, says Dr. Francisco Anaya.

There are two main types of preparation we can use: natural or medicated cycle. In both, there is a first estrogenic phase and a second phase in which we add progesterone, coinciding with the days of development of the embryo to be transferred. Depending on each case, other medications can be added to the preparation (steroids, intralipids, aspirin…), but each case should be assessed individually.

Overview of the two primary types of endometrial preparation for FET:

1. Natural Cycle: This approach involves monitoring the patient’s natural menstrual cycle. Estrogen is produced naturally by the body, and ovulation is triggered using a medication like Ovitrelle. Progesterone is then added to coincide with the embryo’s developmental stage, preparing the endometrium for implantation. This method requires the patient to have regular menstrual cycles and involves regular ultrasound scans to monitor progress.
2. Medicated Cycle: This method mimics a menstrual cycle through medication, allowing for more precise control over timing. It starts with estrogen administration to build the endometrial lining, followed by progesterone. This artificial preparation allows for greater flexibility, making it particularly suitable for patients travelling from abroad, as the schedule can be planned in advance.

Why FET is Convenient

FETs offer significant advantages, especially for patients coming from abroad. In an IVF cycle using our own eggs, if the estrogen level before the egg retrieval is too high, we avoid the risk of the much-feared ovarian hyperstimulation syndrome (OHSS) by using a different trigger medication and postponing the embryo transfer. And, both in IVF and Egg Donation, if the progesterone level is also high, it is advisable to postpone the transfer to increase the chances of success.

For both invasive and non-invasive genetic studies of the embryo, vitrification is also convenient, as we need to wait some days for the results.

And, of course, sometimes, for patients who come from abroad, it is more convenient for their organisation (trips, hotels, work leave…) to have the embryos vitrified and plan a deferred transfer.

Medications for FET Preparation

The protocols for FET preparation primarily depend on whether a natural or medicated cycle is chosen.

Modified natural cycle: This one involves following the patient’s natural cycle with ultrasound scans and, after triggering ovulation with Ovitrelle, adjusting the transfer to the ideal time for the endometrium and for the embryo. In order to be able to go ahead with this preparation, we need the patient to have regular cycles.

Hormone medicated cycle: This one is similar to a menstrual cycle, achieving a pituitary braking and administering hormones in the form of medication (mostly patches or tablets), thus generating an artificial endometrial preparation that will give us greater flexibility when choosing the ideal time for embryo transfer, as we are in control of the cycle. This is the preparation we use most often, especially with patients travelling from abroad, as the trip can be planned in advance, which is not possible in a modified natural cycle.

The Procedure: What to Expect

Once the control ultrasound scans have been carried out, the patient’s lining has achieved optimal thickness and the day of the transfer has been chosen, our embryologists will thaw the selected embryo(s) that same morning. During the waiting period between arrival at the clinic and the embryo transfer, we recommend our patients to drink some water to have a bladder full when it’s time for the procedure. This will facilitate the embryo transfer and allow us to see the embryos in more detail on the ultrasound, as we perform the transfers using ultrasound scan guidance.

The transfer process itself is simple. We perform the procedure in our operating room to have a controlled, sterile environment and to be close to the IVF Lab. Once the embryologist comes in with the catheter, we use a transabdominal ultrasound scan to place the culture medium with the embryo in the best emplacement possible. The patient will feel a sensation similar to a cervical smear test.

After the transfer, the patient will remain for 10-15 minutes resting in the room and then she will be able to resume her daily activities.

Post-Transfer Protocol and Precautions

At UR Vistahermosa we always try to carry out a transfer test on our patients prior to the transfer (usually when they come for a first consultation or tests), which has two fundamental purposes:

1. The patient already knows how the procedure will be performed and will come more relaxed on the day of embryo transfer.
2. We get to know the peculiarities of her cervix and we know which is the best catheter to use to perform the embryo transfer for each specific case.

We recommend taking things easier in the days following the transfer.

Do’s and Don’ts After FET

Do’s:

• Stay Hydrated: Drink plenty of water to stay hydrated.
• Eat a Balanced Diet: Maintain a healthy, balanced diet to support your body.
• Follow Medication Instructions: Adhere strictly to the medication regimen prescribed by your doctor.
• Engage in Mild Exercise: Light activities like walking are beneficial, but avoid anything too strenuous.

Don’ts:

• Avoid Physical Exertion: Refrain from heavy lifting, intense workouts, and other physically demanding activities.
• No Alcohol or Tobacco: Stay away from alcohol, tobacco, and other toxic substances.
• Avoid Immersion Baths: Do not take long baths, use hot tubs, or visit spas.
• Limit Stress: Try to keep stress levels low, as mental well-being is crucial during this period.

 

FAQ – Frequently Asked Questions

The team at UR Vistahermosa put together a helpful list of common patient questions to make it easier for others who are interested in treatment to find the information they need.

What is the Difference Between a Fresh Embryo Transfer and a Frozen Embryo Transfer (FET), and Which is Better for Me?

When considering in vitro fertilisation (IVF) options, understanding the distinction between fresh and frozen embryo transfers is crucial to making informed decisions about your fertility treatment.

Fresh Embryo Transfer

Process:

• Timing: In a fresh embryo transfer, the process begins with ovarian stimulation, where fertility medications are used to encourage the ovaries to produce multiple eggs. These eggs are then retrieved and fertilised in the lab to create embryos. After fertilisation, embryos are transferred to the uterus typically within 3-5 days.
• Cycle Coordination: The transfer occurs within the same menstrual cycle as the egg retrieval, necessitating that the patient’s endometrial lining is ready for implantation shortly after ovarian stimulation.

Benefits:

• Shorter Process: Because there is no need for a freezing step, the treatment cycle is completed quickly. This can be advantageous for those eager to proceed without delay.
• Natural Progression: The immediate use of embryos may be preferred by some patients who want to avoid the additional procedures involved in freezing and thawing.

Drawbacks:

• Hormonal Levels: The ovarian stimulation process often results in elevated hormone levels, which might not be optimal for implantation, potentially affecting the uterine environment.
• Endometrial Synchrony: The endometrial lining must be precisely ready at the time of embryo transfer. If the lining is not optimal, it may reduce the chances of a successful implantation.

Frozen Embryo Transfer (FET)

Process:

• Cryopreservation: After fertilisation, embryos are frozen using advanced cryopreservation techniques, such as vitrification, which allows them to be stored for future use. These embryos can be thawed and transferred in a separate menstrual cycle when conditions are optimal.
• Flexible Timing: FET allows for embryo transfer to be timed with greater flexibility, ensuring that the endometrial lining is in the most receptive state.

Benefits:

• Optimised Conditions: The ability to separate ovarian stimulation from the embryo transfer allows for a more natural uterine environment, improving the chances of successful implantation.
• Reduced Stress: With the timing of the transfer not being immediately tied to the stimulation cycle, there is less hormonal stress on the body, leading to potentially better outcomes.

Drawbacks:

• Freezing Risks: Although vitrification has significantly reduced the risk, there remains a small chance that embryos may not survive the freezing and thawing process.
• Additional Steps: The freezing and thawing process involves more steps and may extend the timeline before transfer can occur.

Which is Better?

The choice between fresh and frozen embryo transfers depends on several factors unique to each patient. Key considerations include:

• Age and Health: Older women or those with specific health conditions may benefit from the controlled timing and potentially higher success rates associated with FET.
• Uterine and Endometrial Conditions: If the endometrial lining is not ideal during the initial cycle, FET provides the flexibility to wait until conditions are optimal.
• Fertility Specialist Guidance: Personalised advice from a fertility specialist is essential to evaluate individual circumstances and determine the most suitable approach.
• Genetic Study of the Embryo: If PGT is performed to the embryos (whether it be to biopsy the embryos in search of aneuploidies, monosomic alterations or perform the non-invasive study of the media culture), the embryos are usually frozen in wait for the genetic results, which can take a few weeks. In these cases, a frozen embryo transfer will be performed once the results are available.

What are the success rates of FET compared to fresh embryo transfer, especially for women over 38?

Understanding the success rates of embryo transfers is vital for managing expectations and planning treatment strategies, particularly for women over 38, who may face additional fertility challenges.

General Trends:

• FET Advantages: Recent research indicates that FET often yields equal or higher success rates compared to fresh transfers. This is largely due to the ability to optimise the timing of the transfer, ensuring better synchronisation between the embryo and the endometrial lining.
• Outcomes: Studies suggest that FET can lead to improved implantation and pregnancy rates, as the uterine environment is less impacted by the hormones used during ovarian stimulation.

Women Over 38:

• Challenges: Women over 38 typically experience a decline in ovarian reserve and egg quality, factors that can significantly influence the success of IVF.
• FET Benefits: For older women, FET can be particularly beneficial as it allows for optimal timing of the transfer and can incorporate genetic screening of embryos to select those with the highest potential for successful pregnancy.

Data Insights

• Research Findings: Studies have shown that FET can result in higher implantation and live birth rates compared to fresh transfers. This is especially true when preimplantation genetic testing (PGT) is used to identify embryos with the greatest potential.
• Clinical Outcomes: Clinics often report FET success rates ranging from 40% to 60%, which can be comparable or superior to fresh transfers, particularly in older age groups.

How are embryos frozen and stored, and how does this process affect their viability for future use?

Cryopreservation techniques play a critical role in preserving embryos for future use, allowing for flexibility and enhanced treatment outcomes.

Cryopreservation Process

Vitrification:

• Technique: Vitrification is a rapid freezing method that prevents ice crystal formation, which can damage cells. This technique has largely replaced slower, more traditional freezing methods.
• Effectiveness: Vitrification ensures that embryos are quickly brought to a solid state, minimising cellular damage and enhancing post-thaw viability.

Storage:

• Conditions: Embryos are stored in liquid nitrogen at temperatures of around -196°C. This extreme cold effectively halts all biological activity, preserving the embryos for an extended period.
• Monitoring: Storage facilities regularly monitor conditions to ensure the long-term viability of stored embryos.

Viability Factors

• Initial Quality: The quality of embryos at the time of freezing is crucial. Higher-quality embryos are more likely to survive the thawing process and retain their developmental potential.
• Lab Expertise: The techniques and expertise of the laboratory staff in handling freezing and thawing processes are critical to ensuring high survival rates.
• Technological Advances: Modern cryopreservation methods have led to significant improvements in survival rates, with many clinics reporting over 95% success in thawing embryos without compromising quality.

What preparation is required for a frozen embryo transfer, and how does it differ from a fresh transfer?

Preparing for an embryo transfer involves specific steps to ensure the best possible conditions for implantation and pregnancy success.

Preparation for FET

Endometrial Preparation:

• Hormonal Treatment: Patients typically receive oestrogen to thicken the endometrial lining and progesterone to stabilise it, creating a receptive environment for the embryo.
• Monitoring: Regular ultrasounds and blood tests are conducted to assess the readiness of the uterine lining, ensuring it is at the optimal thickness and texture for implantation.

Medication Protocols:

• Oestrogen and Progesterone: These hormones can be administered via pills, patches, or injections, tailored to individual needs to prepare the uterine lining effectively.

Differences from Fresh Transfer

• Timing Flexibility: FET offers the advantage of timing the transfer for when the uterine lining is in the best possible state, rather than being tied to the timing of egg retrieval and stimulation.
• Hormonal Stress: Unlike fresh transfers, FET does not involve ovarian stimulation medications, reducing the hormonal burden on the body and creating a more natural environment for the embryo.

Are there specific lifestyle or dietary recommendations I should follow before and after a frozen embryo transfer?

Adopting a healthy lifestyle and diet can significantly impact the success of an embryo transfer and overall reproductive health.

Lifestyle and Dietary Recommendations

Nutrition:

• Balanced Diet: A diet rich in fruits, vegetables, lean proteins, and whole grains supports overall health and hormonal balance. Consider incorporating foods high in antioxidants, such as berries and leafy greens, which may enhance fertility.
• Supplements: Taking prenatal vitamins, including folic acid, can help prepare the body for pregnancy. Omega-3 supplements can support hormonal function and reduce inflammation.

Exercise:

• Moderate Activity: Engaging in regular, moderate exercise, such as walking, swimming, or yoga, can improve blood flow and reduce stress levels. Avoid high-intensity workouts, particularly after embryo transfer, to ensure optimal conditions for implantation.

Stress Management:

• Relaxation Techniques: Incorporate stress-reducing activities such as meditation, yoga, and acupuncture into your routine to promote relaxation and emotional well-being.
• Support Networks: Engage with support groups or seek counselling to manage the emotional aspects of fertility treatment, providing a sense of community and shared experiences.

What are the potential risks and side effects associated with frozen embryo transfers?

While FET is generally a safe procedure, there are potential risks and side effects to be aware of, which should be discussed with your healthcare provider. However, they will be the same risks as when the embryos are transferred fresh. There is no specific risk or side effect directly related to transferring fresh vs frozen embryos.

Potential Risks and Side Effects

• As with any medical procedure, there is a minor risk of infection or injury during the embryo transfer process.

Side Effects from Medications:

• Hormonal Side Effects: Patients may experience side effects from the hormonal medications used in preparing the uterine lining, including mood swings, bloating, and fatigue.

Health Concerns (which are the same as when performing a fresh transfer):

• Ectopic Pregnancy: Although rare, there is a risk of an embryo implanting outside the uterus, which requires medical intervention.
• Miscarriage: The risk of miscarriage exists with both fresh and frozen embryo transfers, influenced by factors such as maternal age and embryo quality.

The problems that we find at embryo transfer do not depend on if we are transferring fresh or frozen embryos. Each case should always be assessed individually, as what works best for one patient may not be ideal for another.

How does the timing of the frozen embryo transfer affect its success, and how is the optimal timing determined?

Timing plays a critical role in the success of FET, with precise synchronisation between embryo development and endometrial receptivity being key.

Timing and Success

Synchronization:

• Implantation Window: The success of FET is heavily dependent on transferring the embryo during the window when the endometrial lining is most receptive. This period is often referred to as the “implantation window.”
• Cycle Monitoring: Hormonal assays and ultrasounds are used to monitor the menstrual cycle and determine the best timing for embryo transfer, ensuring the lining is in optimal condition.

Optimal Timing:

• Hormonal Levels: Blood tests are used to measure hormone levels, ensuring the endometrium is receptive at the time of transfer.
• Ultrasound Assessments: Regular ultrasound checks ensure the endometrial lining is at the ideal thickness and appearance, maximising the chances of successful implantation.

What is the process for thawing embryos, and how does this affect their quality and implantation potential?

The thawing process is a crucial step in FET, impacting the quality and potential success of the embryos used.

Thawing Process

Careful Thawing:

• Gradual Warming: Embryos are thawed gradually to prevent cellular shock, allowing them to rehydrate and resume normal biological functions.
• Cryoprotectant Removal: Cryoprotectants used during freezing are carefully removed to restore embryos to a natural state.

Quality Maintenance:

• Survival Rates: Modern thawing techniques have significantly improved embryo survival rates, with many embryos retaining their pre-freeze quality and potential.
• Post-Thaw Assessment: After thawing, embryos are assessed for cell integrity and development potential, ensuring only viable embryos are selected for transfer.

Can I choose which embryos are used in my frozen embryo transfer, and what factors are considered in embryo selection?

Selecting the right embryos for transfer is a critical decision that involves careful consideration of various factors and should always be a decision made by the assessment of the Embryology Team.

Embryo Selection

Criteria:

• Quality Grading: Embryos are graded based on criteria such as cell number, symmetry, and developmental stage. High-grade embryos are generally preferred for transfer due to their higher implantation potential.
• Genetic Screening: Preimplantation genetic testing can be conducted to select embryos with the greatest chance of resulting in a healthy pregnancy, particularly useful for women over 38.

Patient Involvement:

• Collaborative Decision: Patients are often involved in the selection process, guided by embryologists who assess the viability and potential success of each embryo.
• Personal Preferences: Discussions with the fertility team can help determine the number of embryos to transfer and the criteria used for selection.

How should I manage my expectations and emotions during the FET process, and what support resources are available?

Managing expectations and emotions is an important aspect of navigating the FET process, and there are resources available to support patients through this journey.

Managing Expectations and Emotions

Realistic Expectations:

• Understanding Outcomes: It is important to have a realistic understanding of success rates and potential outcomes, which can help manage expectations and reduce anxiety.
• Preparation: Being prepared for a range of emotions, from hope and excitement to anxiety and disappointment, can aid in navigating the process with resilience.

Emotional Support:

• Counselling Services: Many fertility clinics offer psychological support and counselling to help patients manage the emotional aspects of treatment.
• Support Groups: Joining support groups, either in-person or online, can provide a sense of community and shared experiences. These groups offer a platform to discuss feelings, share success stories, and learn from others facing similar challenges.

Support Resources

• Fertility Clinics: Many clinics provide access to counselling services and support groups to help patients navigate the emotional and practical aspects of fertility treatment.
• Online Communities: Online forums and local groups offer valuable support networks, connecting patients with others who are undergoing similar experiences and providing a sense of community and shared understanding.

In conclusion, Frozen Embryo Transfer offers a flexible and often more convenient option for many patients undergoing IVF. By carefully preparing and adhering to the post-transfer guidelines, patients can optimise their chances for a successful pregnancy. Always consult with your healthcare provider to tailor the preparation and follow-up care to your specific needs.

About the author:

Dr. Francisco Anaya Blanes is experienced in the field of Gynecology and Obstetrics. Currently Gynecologist of the Reproduction Unit of Clinica Vistahermosa. Medical Doctor graduated from the University of Valencia (1993-1999). Specialist degree in Gynecology and Obstetrics (MIR) at the Hospital Clínico de Granada. Master’s degree in Breast Pathology and Senology from the Autonomous University of Barcelona (2003-2004).