Fluorescence in situ hybridization reanalysis of day-6 human blastocysts diagnosed with aneuploidy on day 3.

Objective: To determine the concordance of day-6 blastocyst analysis with the day-3 fluorescence in situ hybridization (FISH) aneuploidy diagnosis.

Design: Retrospective study.

Setting: In vitro fertilization laboratory.

Patient(s): Six hundred sixty embryos were included from 94 IVF/intracytoplasmic sperm injection patients undergoing preimplantation genetic diagnosis.

Intervention(s): None.

Main Outcome Measure(s): Single blastomeres biopsied on day 3. Aneuploidy screening for chromosomes 13, 18, 21, X, and Y were analyzed. Left-over blastocysts were reanalyzed on day 6.

Result(s): Among the 660 embryos evaluated, 367 (55.6%) were euploid and 281 (42.6%) were aneuploid. Of the euploid embryos, 213 embryos were transferred, 68 were frozen on day 5, and 86 were left. All 281 aneuploid embryos were further cultured, and 55 (19.6%) progressed to blastocysts. When FISH reanalysis was performed, 33 of 55 blastocysts (60%) were confirmed aneuploid in concordance with the day-3 diagnosis. However, 22 of 55 blastocysts (40%) were determined to be euploid. In addition, 207 aneuploid embryos (73.7%) arrested before day 6, as opposed to 32 of the 86 euploid embryos (37.2%).

Conclusion(s): Day-3 single-cell embryo biopsy reveals that aneuploidy can be confirmed in 60.7% of the blastocysts on reanalysis. The majority of discordance is most likely due to embryo mosaicism and possibly a limited ability to "self-correct."