Earlier day of blastocyst development is predictive of embryonic euploidy across all ages: essential data for physician decision-making and counseling patients.

PURPOSE: The purpose of this study is to evaluate whether day of blastocyst development is associated with embryo chromosomal status as determined by high-density oligonucleotide microarray comparative genomic hybridization (aCGH).

METHODS: This is a retrospective cohort analysis, including women who underwent in vitro fertilization (IVF) with trophectoderm biopsy at a single private fertility center from January 2014 to December 2014. Repeat cycles were excluded. Cycles were assessed for percentage of blastocysts biopsied on days 5, 6, or 7 and rate of euploid embryos per cycle. Cycles were stratified by Society for Assisted Reproductive Technology (SART) age groups (< 35, 35-37, 38-40, 41-42, > 42) and by donor status.

RESULTS: A total of 388 IVF cycles and 2132 biopsied blastocysts were evaluated. The percentages of blastocysts biopsied on days 5, 6, and 7 were 62.5, 35.8, and 1.7%, respectively. Blastocyst euploid rates on days 5, 6, and 7 were 49.5, 36.5, and 32.9%, respectively. Earlier blastocyst development was associated with a significantly increased euploid rate (p < 0.0001). Younger maternal age (p < 0.0001) and higher number of blastocysts biopsied per patient (p = 0.0063) were both independently associated with greater percentage of euploidy.

CONCLUSIONS: Earlier blastocyst development is independently associated with a higher likelihood of embryonic euploidy in both autologous and donor embryos. In non-biopsied embryos, these data support selection of day 5 blastocysts for transfer over later-developing embryos. These results can assist with patient counseling regarding expectations and outcomes. To our knowledge, this is the first study to examine embryonic euploidy as stratified by both day of blastocyst development and SART age group.