Does slow embryo development predict a high aneuploidy rate on trophectoderm biopsy?

The aneuploidy rates in expanded blastocysts biopsied on days 5 and 6 development were assessed in women undergoing IVF followed by array comparative genomic hybridization. This study included 1171 expanded blastocysts from 465 patients. Among the 465 patients, 215 and 141 underwent embryo biopsy on day 5 and day 6 (46.2% and 30.3%, respectively), and 109 underwent biopsy on both days 5 and 6 (23.4%). The cycles of 206 women were cancelled because only aneuploidy embryos were present (44.3%). The aneuploid embryos were classified according to the type as single, double or complex aneuploidy. No differences were observed in the distributions of these three categories according to the day of the biopsy. The aneuploidy rate was also evaluated according to maternal age, and was found to be higher in older patients; however, no differences in this rate were detected between embryos biopsied on days 5 and 6 according to maternal age. Biopsy was carried out when blastocysts reached the expanded stage. The embryos biopsied on day 6 had a higher rate of aneuploidy (69.9%) than those biopsied on day 5 (61.4%); however, the euploid embryos transferred had similar chances for successful and healthy gestation.