A frozen embryo transfer (FET) is a common fertility treatment where an embryo, previously created through in vitro fertilization (IVF) and cryopreserved, is thawed and placed into a woman’s uterus. Understanding the likelihood of success is a common concern for those undergoing these treatments. Predicting individual outcomes is complex, as success is not guaranteed on the first attempt for everyone.
Understanding Success Rates
Success in the context of frozen embryo transfer is typically measured by the live birth rate, which is the percentage of cycles that result in the birth of a baby. These rates are usually reported per transfer cycle. Data from 2022 indicates that approximately 37.5% of all Assisted Reproductive Technology (ART) cycles, which include FETs, resulted in a live birth delivery. For women under 35 years old using their own eggs, the live birth rate for a first ART cycle was around 32.3%.
For instance, in 2022, the live birth rate for ART cycles was about 37.1% for women aged 35 to 37. This rate decreased to approximately 23.7% for women aged 38 to 40 and further to about 7.6% for women over 40. An overall clinical pregnancy rate of 34.2% was observed in a study analyzing FETs between 2012 and 2022.
Cumulative Success Over Multiple Transfers
While the chance of success for any single frozen embryo transfer can be estimated, the overall probability of achieving a live birth increases with each additional attempt. For women under 40 using their own oocytes, the cumulative live birth rate can reach approximately 68.4% after six cycles of IVF, which includes fresh and frozen transfers.
A study focusing specifically on frozen embryo transfers found cumulative live birth rates of 72.0% after two cycles and 73.3% after three cycles. This illustrates how repeated attempts build on each other. Another analysis from 2006-2012 showed cumulative live birth rates after three cycles were 79% for Day 5 transfers and 66% for Day 3 transfers. For women under 35 years old, this cumulative rate after three cycles ranged from 78% to 82%.
Factors Influencing Success
Several factors play a significant role in determining the success of a frozen embryo transfer. Patient age is a prominent consideration, as maternal age affects both embryo quality and the receptivity of the uterine lining. As women age, the number of eggs and their quality generally decline, which can impact IVF outcomes.
Embryo quality is another important determinant. Euploid embryos, which have the correct number of chromosomes, are more likely to implant and result in a healthy pregnancy compared to aneuploid embryos, which have an abnormal number of chromosomes. Preimplantation genetic testing for aneuploidy (PGT-A) can help identify euploid embryos, potentially increasing success rates.
The condition of the uterus, particularly its receptivity, also influences implantation. Factors such as endometrial thickness are considered, with studies indicating that an endometrial thickness of at least 8 mm can be associated with higher clinical pregnancy rates.
When to Re-evaluate or Consider Alternatives
After multiple unsuccessful frozen embryo transfers, individuals and their medical teams often consider re-evaluating the treatment plan. This re-evaluation typically occurs after 3 to 4 failed transfers, which is a common threshold for exploring other options.
Re-evaluation might involve further diagnostic testing to identify factors contributing to the failures, such as uterine abnormalities or immunological responses. Adjustments to treatment protocols, including medication changes or different embryo preparation techniques, could also be considered.
In some cases, discussions may turn to alternative paths such as considering donor gametes, surrogacy, or adoption. Open and honest communication with the fertility team is important throughout this process, ensuring that all available options and individualized strategies are thoroughly explored.