When undergoing IVF, one of the many questions that can arise is how the grading of embryos impacts the chances of achieving pregnancy. While embryologists use grading to assess embryos’ development, it’s not a perfect predictor of success. We spoke with embryologist Alease Barnes, who shared insights into the complexities of embryo grading and how it can influence decisions in the IVF process.

What Does Embryo Grading Tell Us About IVF Success Rates?

Embryos are graded based on specific criteria, including their development stage, structure, and quality. This helps embryologists determine which embryos may have the highest potential for implantation and pregnancy. However, as Alease explains:

“There isn’t enough correlation for us to say that a really good-quality embryo, like a 4AA, is always going to make a baby, or that a poorer-quality embryo, like a 3CC, won’t.”

While higher-graded embryos generally have a better chance of resulting in a pregnancy, the relationship isn’t absolute. Some embryos graded as “poor” still lead to successful pregnancies, while some “excellent” embryos do not.

Day 5 vs. Day 6 Embryos: Is One Better?

A common question among patients is whether a day 5 embryo is better than a day 6 embryo, assuming they have the same grade. 

Day 5 embryos are typically prioritized in many labs because they have progressed to the blastocyst stage earlier, which is seen as a sign of robust development.

“Clinics will often choose the day 5 embryo,” Alease notes. “Even though research shows that day 5 and day 6 embryos can have similar pregnancy rates, we’re always trying to give patients the very best chance of getting pregnant.”

That said, some labs may choose a day 6 embryo with a higher grade over a day 5 embryo with a lower grade. The choice ultimately depends on the clinic’s philosophy and the specific circumstances of your IVF cycle.

The Role of Embryology Lab Philosophy

Every IVF lab has its own approach to embryo selection. Some labs consistently prioritize day 5 embryos regardless of grading, while others will opt for the embryo with the better grade, even if it developed on day 6. Alease emphasizes the importance of communication:

“It’s always a great idea to reach out to your lab if you’re curious about which embryo they would choose and why.”

By understanding your lab’s practices, you can gain clarity and confidence in the decisions being made about your embryos.

What Should You Take Away?

While embryo grading is a helpful tool, it’s only one piece of the puzzle in determining IVF success. It’s important to remember that:

  • Embryo grades do not guarantee outcomes.
  • Day 5 and day 6 embryos can both result in healthy pregnancies.
  • Communication with your clinic is key to understanding their approach and making informed decisions.

If you have questions about your embryos or lab practices, don’t hesitate to ask your care team. They are there to support you every step of the way. You can slo book in to speak with one of our fertility experts and nurses at Dandi! We can set up a remote call over video chat to go over your questions around the IVF process, your embryo grades, and explore your options.

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