One of the key decisions couples face during IVF treatment is whether to opt for a fresh or frozen embryo transfer. This choice can significantly impact the outcome of the procedure. In a fresh embryo transfer, the embryo is transferred to the uterus shortly after fertilisation, while in a frozen embryo transfer (FET), the embryo is frozen and stored for future use before being thawed and transferred. Both methods have their advantages and disadvantages, leading to an ongoing debate among fertility specialists and patients alike.
This blog aims to share these aspects, providing you with the in-depth knowledge needed to choose the best option between fresh and frozen embryo transfers for your fertility journey.
What is Embryo Transfer?
Embryo transfer is a critical step in the in vitro fertilisation (IVF) process, where an embryo, created by fertilising an egg with sperm in a laboratory, is placed into a woman’s uterus with the goal of achieving a successful pregnancy. This procedure is carefully timed to coincide with the optimal period for implantation, increasing the chances of the embryo successfully attaching to the uterine lining and developing into a healthy pregnancy.
Differences between Fresh and Frozen Embryo Transfers
The primary distinction between fresh and frozen embryo transfers lies in the timing and handling of the embryos.
Fresh Embryo Transfer
In a fresh embryo transfer, the embryos are transferred to the uterus a few days after fertilisation, during the same cycle in which the eggs were retrieved. This means that the embryo transfer occurs shortly after the eggs are fertilised, typically within 3 to 5 days. The advantage of this approach is the immediate use of embryos without the need for freezing and thawing. However, the hormone levels in the body can be quite high due to the medications used to stimulate the ovaries, which can sometimes negatively impact the endometrial environment and the chances of implantation.
Frozen Embryo Transfer
In a frozen embryo transfer (FET), the embryos are frozen and stored for use at a later time. This allows for the transfer to be scheduled during a subsequent menstrual cycle when the endometrial lining is more receptive and hormone levels are more stable. Freezing embryos also provides the flexibility to perform additional genetic testing on the embryos before transfer, ensuring that only the healthiest embryos are selected. The process involves carefully thawing the embryos before transferring them to the uterus, and advancements in freezing techniques have significantly improved the survival rates of embryos through this process.
Hormonal Differences in Fresh vs. Frozen Cycles
The hormonal environment of the endometrium differs significantly between fresh and frozen embryo transfer cycles, impacting the receptivity of the endometrial lining.
Fresh Embryo Transfer Cycles
In fresh cycles, the hormones used to stimulate egg production can result in supraphysiological levels of estradiol and progesterone. These elevated hormone levels can sometimes create a less-than-ideal environment for embryo implantation, potentially hindering success.
Frozen Embryo Transfer Cycles
In contrast, frozen cycles allow for the endometrial lining to be prepared in a more natural state with physiological hormone levels. This often provides a more conducive environment for implantation, as the uterus is not under the same hormonal stress as in fresh cycles.
Fresh vs. Frozen Embryo Transfers: Success Rates
A significant clinical trial involving 2157 women found no substantial difference in live-birth rates between fresh (50.2%) and frozen (48.7%) embryo transfers. This suggests that both methods are similarly effective in achieving live births.
A 2020 study of 36,925 IVF cycles revealed that fresh eggs had a 47.7% live birth rate, compared to 39.6% for frozen eggs. However, when comparing embryos, both fresh and frozen showed comparable success rates, indicating that the method of embryo preservation does not drastically impact outcomes.
Risks or Complications in Fresh and Frozen Embryo Transfers
OHSS is a condition where the ovaries swell and become painful due to overstimulation by fertility medications. Frozen embryo transfers have been associated with a lower risk of OHSS compared to fresh transfers.
Disadvantages of Frozen Embryo Transfers
While generally safe, there are concerns about the survival of embryos during the freezing and thawing process, especially with older slow-freeze techniques. However, with modern vitrification methods, most embryos survive this process.
Disadvantages of Fresh Embryo Transfers
Fresh transfers do not allow time for genetic testing of embryos, which can be a significant drawback for those needing to screen for genetic conditions. Additionally, the hormonal interference from ovulation-inducing medications can sometimes negatively impact the endometrial environment.
Fresh vs. Frozen Embryo Transfers: Health Outcomes
Studies have shown that babies born from frozen embryos have a higher risk of macrosomia (birth weight over 4 kg), which can lead to associated health risks, including a potential increased risk of childhood cancer. However, most babies born from both fresh and frozen embryos are healthy, and long-term health outcomes are generally positive.
In regards to pain during the procedure, the embryo transfer procedure is generally less painful than a pelvic exam and involves minimal cramping or discomfort. Both fresh and frozen transfers are typically well-tolerated by patients.
Multiple Embryo Transfers and IVF Failure
Transferring multiple embryos can increase the chances of pregnancy but also raise the risk of multiple births. It’s not uncommon for only one embryo to implant, even when multiple are transferred.
IVF can fail even with good-quality embryos due to various factors such as uterine issues (e.g., fibroids, polyps, or thin endometrial lining) or genetic and chromosomal issues within the embryos themselves.
Common FAQs: Fresh vs. Frozen Embryo Transfers
Can a frozen embryo split after transfer?
Yes, there is a possibility of zygotic splitting after transfer, which can lead to monozygotic (identical) twins.
How painful is a frozen embryo transfer?
The procedure is generally not painful and involves minimal cramping or discomfort, similar to a pelvic exam.
Do frozen embryos have a higher success rate?
Success rates for frozen embryos are comparable to those for fresh embryos, though they may vary depending on individual factors and specific IVF protocols.
Is a fresh embryo transfer better than a frozen one?
There is no definitive answer; however, fresh transfers offer immediate benefits and potentially higher live birth rates in some cases, while frozen transfers provide a more natural hormonal environment and reduce the risk of OHSS.
Conclusion
Both fresh and frozen embryo transfers have their own sets of advantages and disadvantages. “Fresh transfers offer immediate benefits and potentially higher live birth rates in some cases, while frozen transfers provide a more natural hormonal environment and reduce the risk of OHSS.” Ultimately, the choice between fresh and frozen embryo transfers depends on individual circumstances and medical advice. Consulting with a fertility specialist is crucial to making the best decision for your specific situation.
Are you deciding between fresh and frozen embryo transfers for your IVF journey? Vardaan Medical Centre in Jalandhar, Punjab, is there to help you. With over 22 years of experience and a compassionate approach, we’ve helped 30,000+ couples achieve their dream of parenthood. Our skilled doctors have treated thousands of infertile patients with a success rate of 70–80% in clinical pregnancies.
If you’re seeking expert guidance and personalised care for your IVF treatment, Vardaan Medical Centre is here to support you every step of the way. Book your appointment now at +91 9814021991.
