Embryo Transfer Success Rates – How Successful Is Frozen Embryo Transfer?

Average Frozen Embryo Transfer Success Rates

Due to its high success rates, frozen embryo transfer (FET) is gaining popularity. The FET process involves thawing frozen embryos and transferring them into the uterus during an optimally prepared cycle. International data from fertility clinics indicate that the average success rate per transfer ranges from 30 to 50 percent, depending on individual and clinical factors. Many clinics report higher success rates among younger women or women using genetically tested embryos.

Important factors affecting success are:

• Age of the woman: Women aged under 35 have the highest success rate.
• Embryo quality: Embryos of higher quality, particularly those at the blastocyst stage, typically yield the best implantation rates.
• Endometrial receptivity: A properly prepared uterine lining is essential for good implantation.
• Clinic experience and laboratory conditions: Factors such as advanced thawing and freezing methods significantly impact results.
• Number of embryos transferred: The latest trend in IVF practice is to transfer a single embryo to minimise multiples while still achieving excellent success rates.

In general, FET yields more stable results, as the uterus is not subjected to the hormonal stimulation stress common in fresh cycles.

5-Day Frozen Embryo Transfer Success Rates

Before embryos are frozen or transferred, they are often cultured in the laboratory for several days. A 5-day embryo, also known as a blastocyst, is considered more advanced and has reached the stage where it would naturally be ready to implant.

Reasons for higher success with day-5 embryos (blastocysts):

• The embryos have already demonstrated a critical growth phase.
• The uterine environment during a frozen embryo transfer (FET) is synchronised with the blastocyst's readiness to implant.
• Genetic stability and embryo grading allow embryologists to select the healthiest embryos at this stage.

Typical frozen embryo transfer success rates (for 5-day blastocyst transfer):

• Less than 35 years of age: approximately 50%–60%
• 35 to 40 years of age: approximately 40%–50%
• Greater than 40 years of age: approximately 25%–30%

Therefore, a blastocyst transfer generally offers a better chance of pregnancy than a day-3 embryo transfer, but not all embryos will reach the blastocyst stage, so medical advice should always be followed.

Factors Affecting FET Success Rates

Different factors impact pregnancy outcomes after a frozen embryo transfer. Understanding these factors can enable patients and doctors to maximise every aspect of the treatment.

Key Features Impacting FET Success Rates:

• Maternal Age: Maternal age remains the single biggest contributor. Women under 35 are often more successful because they usually have improved egg and embryo quality.
• Embryo Quality and Stage: Blastocyst-stage embryos with good grading (AA, AB) have an increased potential for implantation.
• Endometrial Health: Endometrial thickness ranging from 7 to 12mm is usually optimal for embryo implantation.
• Lifestyle Factors: Stress, diet, drinking, or smoking can negatively impact the success rate. Thus, lifestyle factors must be closely monitored.
• Fertility Clinic Expertise: Success rates can also vary between fertility clinics due to the technology of the laboratory, the experience of the embryologists, or the methods of cryopreservation.

Additional Insights:

• If you are using genetic testing (PGT-A) to choose chromosomally normal embryos, success rates can be improved.
• In some women, immunological factors may inhibit acceptance of the embryo.

Tips to Improve Frozen Embryo Transfer Success

Apart from medical precision, patient involvement and care can also significantly influence FET outcomes. A holistic and mindful approach, both before and after the procedure, can enhance the body’s readiness for implantation.

Some Helpful Tips:

• Eat a healthy diet: Consume a balanced diet. Include foods rich in antioxidants, iron and folate in your diet.
• Do not smoke or drink: Smoking or drinking can have a negative impact on fertility and embryonic quality.
• Stay physically active: Mild yoga, walking and breathing exercises promote increased blood circulation to the uterus.
• Eliminate or reduce stress: Meditation, counselling or support groups can help with emotional health.Follow the doctor's orders closely: Hormonal medications and progesterone will be essential to prepare the uterine lining.
• When possible, transfer blastocysts: 5-day embryos generally have overall better success rates.
• Rest and hydrate: It is important to rest, especially after transfer, to support uterine receptivity.

These tips complement medical treatment and contribute to a calm, supportive environment for embryo implantation.

Conclusion

Frozen embryo transfer (FET) represents a significant advance in assisted reproduction. Typically, pregnancy rates range from 30-50% per transfer (with higher rates in women under 35 or in blastocyst transfers), making it a safe, highly effective, and patient-friendly alternative to conception. Compared to fresh embryo transfers, FET enhances uterine receptivity, reduces hormonal stress, and leads to more predictable transfer outcomes.

Individual outcomes depend on the patient's age, health, and the clinic's experience. Therefore, couples are encouraged to work with fertility specialists to discuss personalised plans to optimise their chances of success.