Pregnancy Rates Significantly Decline with Biopsy after Day 5 and a Decrease in Embryo Grade

To compare whether trophectoderm biopsy day or embryo quality have an effect on pregnancy rates after transfer of embryos which underwent pre-implantation genetic testing for aneuploidy (PGT-A) using next-generation sequencing (NGS). Retrospective data analysis of laboratory and clinical outcomes following PGT-A and frozen embryo transfer. Patients who underwent a frozen euploid single embryo transfer between January 2016 and December 2017 at a single laboratory were assessed. Embryos were cultured to the hatching blastocyst stage (HB) and assigned an overall grade of good, fair or poor. Only HB embryos that were of good or fair quality underwent trophectoderm biopsy on day 5 or 6 with subsequent PGT-A using NGS for genetic results. Chi-square was used to compare differences between groups and a multivariate logistic regression was used to adjust for embryo biopsy day, embryo grade as well as oocyte age. P< 0.05 was considered statistically significant. 514 women underwent a total of 581 frozen single euploid embryo transfers. The mean oocyte age was 34.6 years and the overall pregnancy rate was 62.3%. 71% of embryos were biopsied on day 5 and 68% percent of all of the embryos were of good quality at biopsy. A significant overall reduction in pregnancy rates was seen (67.3% down to 50.9%) as the day of biopsy increased and the quality of the embryo declined (p=0.013; Table 1). Although, there was a 6.6% decline in pregnancy rate between day 5/fair and day 6/good embryos, no significant difference was able to be determined due to limited samples in each transfer group (p= 0.43). Additionally, while there was a 9.7% decline in pregnancy rates between day5/fair and day 6 embryos of good or fair quality, this was also not significantly different (p= 0.16). These findings demonstrate that as embryos require longer to grow to a biopsy stage or are of less quality, the overall pregnancy rates significantly decline. Although each step down in embryo quality and advancing day of biopsy results in at least a 5% decrease in pregnancy, a much larger sample size will be required to detect these differences significantly. Additionally, our data suggest that delaying biopsy to potentially improve embryo quality does not result in a significant increased pregnancy rate. Overall, our data can be of use in deciding which embryos to biopsy, on which day of development, as well as guiding patients in setting expectations for transfer outcomes from euploid embryos.Tabled 1Embryo biopsy day and grading characteristics associated with pregnancy outcomesDay of embryo biopsyGrade of embryo biopsyPregnancy (Rate)Mean oocyte age, years (SD)5HB-Good224/333 (67.3%)34.1 (4.9)5HB-Fair48/77 (62.3%)34.6 (5.3)6HB-Good34/61 (55.7%)34.2 (5.3)6HB-Fair56/110 (50.9%)34.9 (5.3) Open table in a new tab