Day 3 or Day 5 embryo transfer—what’s the difference? Learn about the timing, pros, and cons of each option for IVF success.
Introduction
The timing of embryo transfer—Day 3 or Day 5—is an important decision during IVF treatment. Advances in embryo culture media have led to a shift in the IVF practice from cleavage‐stage embryo transfer to blastocyst‐stage embryo transfer. Many wonder which day offers the highest chance of success. Day 3 transfers involve embryos at an earlier cleavage stage, while Day 5 embryos have reached the blastocyst stage.
Both approaches have their pros and cons, and the decision often depends on individual factors, including embryo quality and the specific IVF protocol. Let’s dive into the article to understand the difference between these two options can help you and your doctor choose what’s best for your journey
Day 3 Embryo Transfer: What You Need to Know
- A Day 3 transfer involves transferring the embryo when it has around 8 cells. At this stage, the embryo is still developing, and many clinics offer this option if fewer embryos are available or if there is a need to see which ones will develop further.
- A key benefit is that the transfer happens sooner, which can be preferable in some cases. However, the embryo is less developed, and some studies suggest that it might not offer the same implantation success rate as a Day 5 transfer.
- According to National Library of Medicine, Day 3 transfers are less common, but they remain a valid choice depending on the individual case.
Day 5 Embryo Transfer: The Blastocyst Stage
- The rationale for blastocyst‐stage transfer is to improve both uterine and embryonic synchronicity and enable self selection of viable embryos, thus resulting in better live birth rates.
- By Day 5, embryos have developed into a blastocyst, a stage with more advanced cell structures. This development often results in a higher likelihood of successful implantation, as the embryo is closer to the stage it would naturally be in before reaching the uterus.
- Additionally, transferring on Day 5 allows embryologists to better select the most viable embryos. However, not all embryos survive to this stage, which can limit the number of embryos available for transfer.
Which Is Right for You?
- The decision between Day 3 and Day 5 transfers is based on multiple factors, including the number of embryos available, their quality, and the specific IVF protocol.
- If a patient has a limited number of embryos, a Day 3 transfer might be preferred to give more embryos a chance at implantation. Conversely, if several healthy embryos are available, waiting until Day 5 could increase the chance of selecting the one most likely to result in a pregnancy.
- Your fertility specialist will guide you through these options, taking into account your unique situation.
Day 3 Embryo Transfers: Advantages vs Disadvantages
Advantages:
- Quicker process: Suitable for patients needing immediate transfer due to medical conditions.
- Viable for limited embryos: Useful when fewer embryos are available that might not develop to Day 5.
- Early replacement in the uterus may be better for embryo growth by limiting the time spent in the in vitro environment of the embryology laboratory.
Disadvantages:
- Lower success rates: Embryos are less developed, reducing implantation chances.
- Increased abnormal or mosaic embryos: A large proportion of morphologically‐normal day 3 embryos are chromosomally abnormal or mosaic (having components of both normal and abnormal cells)
- Limited information: Embryologists have less time to evaluate embryo quality.
A British Medical Journal (BMJ) study reported that Day 3 transfers have a slightly lower success rate compared to Day 5 transfers, but they still offer a viable chance for pregnancy in many cases.
Day 5 Embryo Transfers: Advantages vs Disadvantages
Advantages:
- Higher success rates: Improved implantation due to embryo’s advanced development.
- Better selection: Additional days allow embryologists to choose the most viable embryos.
- Decreased chromosomal abnormalities: Day 5 embryos have lesser mosaicism and decreased genetic abnormalities.
Disadvantages:
- Embryo loss risk: Some embryos may not survive until Day 5.
- Emotional impact: Fewer embryos available for transfer or cycle cancellation due to no formation of blastocysts can be disheartening.
The same BMJ study highlighted that while Day 5 transfers have a higher success rate, fewer embryos may be available for transfer due to the natural selection process.
Conclusion
According to the Cochrane database, the largest study done to differentiate between day 3 and day 5 embryos, they found that there is low-quality evidence that a blastocyst transfer is associated with higher pregnancy rates. They also found moderate-quality evidence showing that clinical pregnancy rates are higher with fresh blast transfers. Both options have advantages depending on the number and quality of embryos available.
The decision between a Day 3 or Day 5 embryo transfer should be made in consultation with your fertility specialist, who will consider your specific case.
Ref: Glujovsky D, Quinteiro Retamar AM, Alvarez Sedo CR, Ciapponi A, Cornelisse S, Blake D. Cleavage-stage versus blastocyst-stage embryo transfer in assisted reproductive technology. Cochrane Database Syst Rev. 2022 May 19;5(5):CD002118.
FAQs:
- How do I know which day is best for my embryo transfer?
The best day for embryo transfer depends on your individual circumstances, including the number and quality of embryos available. Your fertility specialist will help you decide based on your IVF plan.
- What is the main difference between Day 3 and Day 5 embryo transfers?
Day 3 embryos are at the cleavage stage, while Day 5 embryos have developed into blastocysts, which are more advanced in their growth and may have a higher implantation rate.
- Why might a doctor recommend a Day 3 embryo transfer?
A Day 3 transfer might be recommended if there are fewer embryos available, allowing the doctor to transfer them earlier and give them a chance to develop in the uterus.
