During the initial stages of in vitro fertilization (IVF), fresh embryo transfer was the only option available. This is because the technology of cryopreservation—the freezing of embryos for later use—was in its early stages. In the 40 years after the first embryo was successfully transferred, cryopreservation techniques, culture media (the environment in which the embryo grows), and advanced reproductive technology have advanced dramatically, making fresh and frozen embryo transfers (FETs) readily available. FETs are presently the favored transfer type, however both are used often.
The Difference Between Fresh and Frozen Embryo Transfer
Frozen and fresh embryo transfers both start with ovulation induction and monitoring. When the uterus is ready, the woman will have an egg retrieval, in which the reproductive endocrinologist will fertilize her eggs with her partner’s or sperm donor’s sperm.
Once the eggs and sperm have been collected and fertilized, a fresh embryo transfer will take place three to five days later, placing the fertilized embryo back into her uterus.
In contrast, a frozen embryo transfer (FET) can take place years after a woman’s egg retrieval and sperm fertilization. During a FET, your fertility specialist will implant a thawed embryo into the woman’s uterus in the hopes of a successful conception.
Fresh embryo transfer process step by step
- A fresh embryo transfer usually takes place 5 days after a patient’s eggs are extracted.
- The eggs are fertilized with sperm in the laboratory, and the resulting embryo is carefully observed.
- The main advantage of a fresh embryo transfer is a shorter time to conception, as there is only a 5-day wait between egg retrieval and embryo transfer back into the uterus.
NOTE: There are several contraindications to a fresh IVF transfer. If a patient’s progesterone level is high, a fresh transfer should be avoided since it will have a negative impact on embryo implantation. Similarly, if a patient is at risk of hyperstimulation due to the medications used to enhance egg maturation, a fresh transfer may be risky.
Frozen embryo transfer process step by step
- During the FET cycle, your embryos are frozen and transferred to your uterus.
- This is done when your menstrual cycle is most favorable for pregnancy.
- An IVF frozen embryo transfer typically takes place 6-8 weeks after the embryo is frozen.
- Once the patient is prepared for the transfer, she is given medications that imitate a natural menstrual cycle, and the FET date is timed to coincide with the cycle for optimal implantation.
Benefits of Frozen Embryo Transfer
- If the patient chooses to have her embryos examined for genetic problems, a FET is necessary. Preimplantation genetic testing (PGT) occurs immediately after egg retrieval. The embryo is biopsied by taking a small sample of the embryo’s DNA and evaluating it for chromosomal and genetic abnormalities. Once PGT is complete, the embryologist can select only chromosomally healthy embryos for transfer. Transferring just the normal embryos improves pregnancy success significantly.
- Freezing an embryo can also be useful for additional pregnancies years later because embryos can be preserved indefinitely.
- With FET, you won’t need to go through another egg retrieval operation because you already have a batch of embryos ready to use. The only medications you’ll need to consider are those that help thicken your uterine lining in preparation for your embryo transfer, lowering the stress on your body.
- If a patient desires to maintain fertility due to age, cancer treatment, or other reasons, frozen embryos can be generated for later use.
When does frozen transfer work best?
In some cases, frozen embryo transfer may be the best alternative, including the following:
High progesterone levels: When progesterone levels are high during egg extraction, the window of uterine receptivity is more likely to shift forward. In these circumstances, it is often preferable to store the embryos and then transfer them when the uterus is receptive again.
Polycystic ovary syndrome (PCOS): Research has shown that women with PCOS benefit more from frozen versus fresh transfer. Frozen transfer lowers the risk of ovarian hyperstimulation syndrome (a consequence of egg retrieval) and increases the likelihood of maintained pregnancy.
Embryos requiring genetic testing: Genetic testing of embryos is time-consuming. As a result, by the time a verified embryo is prepared for transfer, the window of uterine receptivity will most likely have closed. In this situation, frozen embryo transfer is usually preferable.
Frozen and Fresh embryo transfer success rate
When it comes to success rates, both FET and fresh need to investigate a variety of parameters. When determining whether to freeze your embryos or pursue a fresh transfer, you should examine your age or the age of the donors during embryo freezing, the quality of the sperm used for fertilization, and your overall health during both transfers.
- Greater quality embryos are linked to a greater live birth rate.
- However, poor-quality embryos are linked to a low birth rate.
- If you opt to freeze your embryos or participate in a fresh embryo transfer before the age of 35, your chances of getting higher-quality embryos improve.
- However, if you opt to freeze your embryos or participate in a fresh transfer after the age of 35, the odds of getting low-quality embryos increase.
So, regardless of whether you transfer fresh or frozen embryos, your age will play an important role in producing high-quality embryos. Now that we’ve identified the success percentages, let’s look at the advantages of FET versus new transfers.
FAQ’s
What are the factors to consider when opting for fresh embryo transfer?
Fresh embryo transfer refers to the immediate transfer of embryos into the uterus following an IVF round. Here are some crucial points to consider:
1. Timing: Embryos are transferred immediately after fertilization in the same IVF cycle.
2. Embryo Quality: Fresh embryos are usually of great quality as they are selected soon after fertilization.
3. Improved Synchronization: Fresh transfers coincide with the natural monthly cycle, which may improve embryo-uterine synchrony.
4. Hormonal Stimulation: During fresh cycles, ovarian stimulation may cause ovarian hyperstimulation syndrome (OHSS) in some individuals.
What are the factors to consider when opting for frozen embryo transfer?
Frozen embryo transfer refers to the cryopreservation (freezing) of embryos for later use. Here are some crucial points to consider:
1. Delayed Transfer: Embryos are frozen and transferred in the following menstrual cycle or later, providing flexibility.
2. Survival Selection: Only embryos that have survived the freezing and thawing process are transferred, assuring their hardiness.
3. Hormonal Stimulation: FET normally uses lesser hormone stimulation, lowering the risk of OHSS.
4. Cycle Preparation: FET enables careful management of the uterine lining, potentially improving implantation.
How does choosing either fresh or frozen embryo transfer impact the IVF process?
Choosing between fresh and frozen embryo transfer can influence the IVF timeframe, the requirement for and extent of hormone treatment, and the strategy for embryo management. Fresh transfers necessitate precise timing within the natural or induced menstrual cycle, but frozen transfers provide greater scheduling flexibility and may allow for extra embryo testing, such as preimplantation genetic testing (PGT), before transfer.
Can the decision to transfer embryos have an impact on the health of the baby?
Current research shows that both fresh and frozen embryo transfers can result in healthy pregnancies and infants. Some studies imply that the two approaches produce different birth outcomes, but additional research is needed to fully understand this. The objective is to select the transfer procedure that would provide the mother the highest possibility of having a successful and healthy pregnancy. To know what is best for you, consult with a fertility specialist.