Background: PGD (preimplantation genetic diagnosis) for the purpose of aneuploidy screening (AS) has increased in usage over the past decade and is usually performed 3 days after oocyte retrieval. Our ART program currently performs AS on approximately twenty percent of patients requiring IVF-ET, and embryo biopsy was typically performed on virtually every embryo generated from these patients, regardless of their rate of cleavage or “grade” at biopsy.

Objective: The aim of the study was to determine if slow cleaving, poor grade embryos are more likely to be chromosomally abnormal, and if biopsy of these embryos is either of value or is in fact a waste of medical resources.

Materials and Methods: A retrospective analysis was performed on data collected from consecutive patients requesting aneuploidy screening of their embryos over a five month period. Morphological grading of embryos as well as their PGD results was recorded.

Results: Out of 683 embryos biopsied from one hundred and eleven patients, 113 (16%) were < 6 cells at the time of biopsy on day three. Seventy four of 113 (or 65%) of these embryos were aneuploid. Further analysis of these embryos revealed a roughly equal distribution of normal versus aneuploid (26 vs. 30) outcomes if the grade of the embryos was in the A-B (good) range. In contrast, slow-cleaving embryos in the C-D (poor) morphologic range were five times as likely (11 normal vs. 55 aneuploid) to be abnormal in their chromosomal makeup, as well as three times as likely to have anucleated blastomeres (16 of 22) as did good grade, albeit slow-cleaving embryos.

Conclusion: This data suggests it is reasonable to biopsy <6 cell embryos on day three post-insemination if they are of good morphology. Slow-cleaving, morphologically compromised embryos are almost always aneuploid, and as these embryos invariably arrest upon extended culture, not performing AS on this subset of embryos poses little risk of discarding healthy, euploid embryos capable of establishing a sustained pregnancy, and has the added benefit of conserving valuable medical resources.

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