Embryo Grading FAQ

Embryo grading and selection is a highly nuanced process that plays a critical role in fertility treatment. This process involves evaluating embryos based on a range of factors, including their appearance, rate of development, and cellular structure, to determine which have the highest potential for implantation and healthy development.

At Boston IVF, our experienced fertility specialists combine their expertise with cutting-edge technology to meticulously assess each embryo, ensuring the most informed decisions are made.

Below, we address some common questions patients have about embryo grading to help you better understand this essential step in the fertility journey.

When going through the IVF process, one of the most important steps is selecting which embryo to transfer. Understanding how embryos are graded can help demystify this crucial part of your fertility treatment. Dr. Kristen Wright of Boston IVF shares insights on embryo grading and what it means for your IVF success.

What is Embryo Grading?
Embryo grading is a process used to assess the quality of embryos during an IVF cycle. This helps fertility specialists decide which embryos have the best chance of leading to a successful pregnancy. Embryos are graded based on several factors, including how well they’ve developed and how they look under a microscope. Grading typically happens at two stages:

✓ Day 3 (Cleavage Stage): By Day 3, embryos should have between 6 to 10 cells. The grading focuses on the number of cells and how many fragments (broken-off pieces) the embryo has. A-grade embryos have no fragments, while lower grades indicate more fragmentation.

✓ Day 5 or 6 (Blastocyst Stage): At this point, the embryo has developed into a blastocyst, which has two distinct cell types—the inner cell mass (which becomes the baby) and the trophectoderm (which forms the placenta). Embryos are graded based on the size and quality of these cells.

What Do the Embryo Grades Mean?
Embryos are graded using letters and numbers to indicate their quality. For example, a "4AB" embryo means:

✓ The number "4" refers to how expanded the blastocyst is (a higher number means more advanced development).

✓ The first letter "A" refers to the quality of the inner cell mass.

✓ The second letter "B" refers to the quality of the trophectoderm.

✓ Letter grades range from A to D, and while A grade embryos are preferred, B and C embryos can still result in successful pregnancies.

What is PGT-A Testing and How Does It Relate to Embryo Grading?
PGT-A (Preimplantation Genetic Testing for Aneuploidy) is a test that screens embryos for chromosomal abnormalities. This helps identify embryos that may not develop into a successful pregnancy. While grading looks at the embryo’s physical appearance, PGT-A looks at its genetic makeup. PGT-A tested embryos with normal chromosomes have a higher likelihood of successful implantation, regardless of their grade.

Should I Do a Day 3 or Day 5 Transfer?
Most IVF clinics now prefer to transfer embryos at the blastocyst stage (Day 5 or 6) because they have a better chance of implanting successfully. However, in cases where few embryos are available or previous cycles have shown poor blastocyst development, a Day 3 transfer may be considered.

How Many Embryos Should Be Transferred?
In most cases, single embryo transfer (SET) is recommended, especially when using high-quality or PGT-A tested embryos. Transferring multiple embryos increases the risk of a twin or multiple pregnancy, which carries higher risks for both the individual carrying the pregnancy and the babies. However, there may be situations where transferring more than one embryo makes sense, depending on your unique circumstances.

Can Lower-Grade Embryos Lead to a Successful Pregnancy?
Yes, lower-grade embryos can still result in successful pregnancies. While A-grade embryos have a higher success rate, B and C grade embryos are often transferred with success. Additionally, sometimes embryos graded lower can still implant and successfully develop into babies.

What Happens if My Embryo Doesn’t Implant?
If a high-quality embryo doesn’t result in a pregnancy, it’s often due to factors outside of the embryo itself, such as uterine conditions or immune responses. If you’ve had several failed transfers, your fertility specialist may recommend additional testing to check for underlying issues in the uterus.

If you want to learn more about embryo grading, Boston IVF specialists are here to guide you through the process and address your questions!