Embryo Success Rates [Day-by-Day Breakdown]

KEY POINTS:

• Embryo transfer success rates vary by day, with the highest chance of success typically occurring on day five.
• Generally, the earlier the transfer, the lower the success rate.
• Not all embryos make it to day five or beyond, making careful planning and flexibility essential for a successful outcome.

Over seven days, embryos progress through different stages, each with its own success rate.

Understanding how embryos develop can help you decide the best time to schedule a transfer.

 In this article, we’ll focus on clinical pregnancy rates: the chances of a positive pregnancy test after an embryo transfer.

Below, we’ll break down embryo development across days two through seven and explore how success rates change. If you’re ready to take the next step, fill out our form to connect with a reputable fertility clinic near you.

Day 2 Embryo Transfer Success Rates

Clinical Pregnancy Rate: About 25%

Day two embryos, also known as cleavage-stage embryos, consist of just a few cells. At this point, the embryos have just started dividing.

While one study reports a clinical pregnancy rate of 26% for these embryos, early transfers are uncommon. Most clinics prefer to wait longer to better monitor the embryo’s development because day two embryo transfer success is low. Between days two and three, embryos typically double or triple in size. This gives embryologists more information to assess their viability.

Day 3 Embryo Transfer Success Rates

Clinical Pregnancy Rate: About 40%

According to one research paper, the day three embryo success rate is 42.3%. In the past, day-three transfers were more common because many believed the uterus provided the best environment for continued growth. However, with advances in lab technology, clinics can grow embryos to later stages before transfer.

On day three, embryologists can grade embryos based on three key factors:

Day 4 Embryo Transfer Success Rates

Clinical Pregnancy Rate: About 50%

On day four, the embryo reaches the morula stage, where the cells compact into a tight cluster resembling a berry. Research indicates that the clinical pregnancy rate for day four embryos is 49.7%. The four-day embryo transfer success rate is a marked improvement from earlier stages, but it’s still not as high as day five.

Because day five embryos have a higher chance of success, many clinics prefer to wait another day to maximize your chances. However, if the embryo seems well-developed on day four, your doctor might decide that it’s time to transfer.

Day 5 Embryo Transfer Success Rates

Clinical Pregnancy Rate: About 60%

By day five, the embryo has reached the blastocyst stage. Blastocysts are made up of hundreds of cells forming two main structures: the inner cell mass (which will develop into the fetus) and the trophectoderm (which becomes the placenta).

At this stage, embryologists can grade the embryo based on:

Research shows that the day-five embryo success rate is 61.3%. Because the embryo is more developed, transferring on day five provides a better chance of implantation and pregnancy.

Discover more about surrogacy with frozen embryos. If you already have embryos ready for transfer, contact us today to get matched with a surrogate.

What Are the Odds of an Embryo Making It to Day 5?

Unfortunately, not all embryos make it to day five. In fact, Reproductive Medicine Associates estimates that only 30% to 50% of embryos reach the blastocyst stage. The ability to develop to this point largely depends on the quality of the embryo.

Day 6 Embryo Transfer Success Rates

Clinical pregnancy rate: About 55%

If an embryo hasn’t quite reached the blastocyst stage by day five, your doctor might suggest waiting until day six. At this point, the embryo is still a blastocyst, but it has had an extra day to develop. The clinical pregnancy rate for day six embryo success is 54.2%, which is still high.

In some cases, waiting until day six makes more sense. If an embryo needs more time to mature, holding off for one extra day can give it the best chance of successful implantation.

Do All Day 5 Embryos Make It to Day 6?

Not all embryos that make it to day five will survive to day six. The blastocyst stage is complex, and some embryos might never develop. If they never reach the blastocyst stage, then they aren’t viable for implantation.

Day 7 Embryo Transfer Success Rates

Clinical Pregnancy Rate: >15%

By day seven, the chances of success drop dramatically. Research shows that the clinical pregnancy rate for day seven embryos is only 13.9%. These embryos are referred to as extended blastocysts. While they can still be transferred in certain cases — such as when synchronization with the uterus is crucial — they aren’t usually the first choice due to the low day-seven embryo success rate.

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Even with a high chance of success on days five or six, it’s important to remember that not all embryos will result in a pregnancy. If you’ve tried in vitro fertilization and are still struggling to conceive, other family-building options like gestational surrogacy could be worth exploring.

Whether you’re ready to move forward or just need more information, reach out to us to explore your options. You don’t have to navigate this journey alone — we’re here to help you every step of the way.