Embryo Grading in IVF: What the Numbers and Letters Mean

What does the evidence say about embryo grading in ivf?

1. The Gardner scale describes blastocyst expansion and hatching with a numerical stage. It also assesses the inner cell mass and trophectoderm. These are different observations, so reading only the number leaves out part of the laboratory description. 1
2. Embryology laboratories document development and use defined procedures for assessment and selection. Ask which grading system your clinic uses and when the observation was recorded. A result should be interpreted within that laboratory's workflow. 2
3. PGT-A analyzes sampled cells for chromosome-number findings. Morphology is a visual assessment. A visually favorable embryo is not automatically euploid, and a chromosome result should not be inferred from a grade such as 4AA. 3
4. Embryo quality is one part of transfer planning, along with age, testing, previous outcomes, and medical history. A less favorable appearance does not by itself establish that transferring additional embryos is the best next step. 4
5. Embryos develop through stages after fertilization before transfer or storage. Not every retrieved egg becomes an embryo available for transfer. Ask for a stage-by-stage account without equating the initial egg count with the final embryo count. 5

When should you review the embryo grading report?

• After fertilization, ask when the next development update will be available.
• Before transfer, interpret appearance together with the complete embryo and clinical history.
• Keep the laboratory legend with your report when seeking another opinion.

Questions for your fertility or prenatal team