When undergoing IVF, hearing that you have a "high-quality" embryo can bring a sense of hope and optimism. But what happens when that high-quality embryo doesn’t result in a successful pregnancy? In the latest installment of her embryo grading series, embryologist Alease Barnes sheds light on this common question, breaking down why embryo grading, while helpful, doesn’t tell the whole story.
What Embryo Grades Actually Mean
Embryos are graded based on their appearance—how they look under the microscope. Terms like 5AA indicate specific features of an embryo’s development and structure. However, it’s important to know that these grades reflect morphology, or visual quality, and don’t necessarily indicate whether an embryo is genetically normal.
“Just by looking at the embryo, we can’t see if it’s genetically normal or not,” explains Alease. “Even though an embryo is graded highly, like a 5AA, that doesn’t guarantee it’s free from genetic abnormalities.”
The Role of Genetic Testing (PGT-A)
The only way to determine if an embryo has chromosomal abnormalities is through Preimplantation Genetic Testing for aneuploidy (PGT-A). This test screens embryos for conditions like Down syndrome, trisomy 18, and other chromosomal disorders. It’s worth noting that these abnormalities often occur spontaneously during embryo development and aren’t necessarily inherited from the parents.
Without PGT, even a visually “perfect” embryo could carry a genetic abnormality that prevents implantation or leads to an early miscarriage. According to Alease, the most common reason high-quality embryos fail to implant is due to these undetectable genetic issues.
Does Embryo Grade Correlate with Pregnancy Success?
While embryo grades help embryologists choose the best candidates for transfer, they’re not a guarantee of success. Alease notes:
“Most embryos have about a 50% chance of pregnancy, regardless of grade, depending on factors like the lab, the patient, and the clinic’s practices.”
Higher-quality embryos may have a slightly better chance of leading to pregnancy, which is why they’re prioritized for transfer. But even lower-graded embryos can result in healthy pregnancies and beautiful babies.
“If your embryologist thought the embryo was good enough to freeze, we also believe it’s good enough to transfer,” Alease reassures.
Assisted Hatching: Does It Improve Success Rates?
Another factor patients often ask about is assisted hatching—a process where embryologists create a small hole in the embryo’s outer layer (zona pellucida) to help it “hatch” and implant. While this technique doesn’t harm embryos, research on its effectiveness in improving pregnancy rates is mixed. Many clinics perform assisted hatching routinely, as it might help in some cases, but it’s not a guaranteed way to increase success.
Key Takeaways for IVF Patients
A high-quality grade doesn’t always mean a genetically normal embryo, and lower-grade embryos can still lead to healthy pregnancies.
PGT can offer insights into chromosomal health but is an optional step in the IVF process.
If your lab chose to freeze an embryo, it’s considered viable for transfer.
Embryo grading is just one piece of the puzzle in the IVF journey. While it can guide decision-making, success ultimately depends on a combination of factors, including embryo genetics, uterine health, and the expertise of your clinic.
