Is a 5AA a “good” embryo? What about 4AB? These embryo gradings may sound cryptic, and we’re here to help you understand what embryo grading is and how it can predict an embryo’s chance of success.
By women’s health expert Halle Tecco, MPH, MBA
If you are going through IVF, you may have received an embryo report outlining the “grades” of your embryo(s). These can be difficult to decipher, so we’ve written this guide to walk you through how embryologists come up with this grade and what it means for your chances of success.
How are IVF embryos graded?
The Gardner Embryo/Blastocyst Grading System is a common way embryologists grade embryos to determine their development and ultimately potential for success. The system has three parts, a letter and two numbers (e.g. 4AA, 2BA, 5AB). Let’s walk through each part:
- Blastocyst development stage: 1–6 (with 5 being the most developed)
- ICM quality: A — C (A being the best)
- TE Quality: A — C (A being the best)
Let’s start with the number, 1–6. This number indicates the blastocyst development stage, or the degree of the expansion of the embryo’s cavity.
- 1: Early blastocyst — the blastocele is less than half the volume of the embryo.
- 2: Blastocyst — the blastocele is greater than or equal to half of the volume of the embryo.
- 3: Full blastocyst — the blastocele completely fills the embryo.
- 4: Expanded blastocyst — the blastocele volume is larger than that of the early embryo and the zona pellucida is thinning.
- 5: Hatching blastocyst — the trophectoderm has started to herniate through zona pellucida.
- 6: Hatched blastocyst — the blastocyst has completely escaped from the zona pellucida.
Want to learn more? Read the full article on Natalist.com.
