Association between day of trophectoderm biopsy and outcomes of euploid embryo transfers

To compare clinical outcomes following transfer of euploid blastocysts biopsied on day 5 with those of embryos deemed unsuitable for biopsy on day 5 and that were biopsied on day 6. Retrospective cohort study. Warmed NGS-tested euploid single embryo transfers from autologous IVF cycles performed at our center from 10/2015 to 2/2020 were included. Implantation rates (IR) and ongoing pregnancy rates (OPR) beyond 12 weeks gestation were assessed. Transfers were grouped by blastocyst quality (good, fair and poor) and then stratified by day of biopsy. Relative risks (RR) and 95% confidence intervals (CI) were calculated within each blastocyst quality class using log-binomial regression adjusting for age. GEE modeling was used to account for patients contributing multiple cycles. 237 transfers from 191 patients were analyzed. See table below.Tabled 1Blastocyst qualityDay Biopsy/ETNo. of transfersIR (%)RR (95% CI)OPR (%)*RR (95% CI)Good51715/17 (88.2%)ref14/17 (82.3%)ref62115/21 (71.4%)0.86 (0.67, 1.10)13/20 (65.0%)0.85 (0.64, 1.13)Fair511782/117 (70.1%)ref68/112 (60.7%)63527/35 (77.1%)1.09 (0.91, 1.31)21/34 (61.8%)1.03 (0.86, 1.23)Poor52216/22 (72.7%)ref12/22 (54.6%)ref6259/25 (36.0%)0.69 (0.53, 0.88)8/25 (32.0%)0.81 (0.63, 1.04)Any5156113/156 (72.4%)ref94/151 (62.3%)ref68151/81 (63.0%)0.90 (0.74, 1.08)42/79 (53.2%)0.88 (0.69, 1.11)*data missing for 7 patients Open table in a new tab *data missing for 7 patients Both the IR and OPR were increased for embryos biopsied on day 5 compared to those biopsied on day 6 when combining all transfers regardless of blastocyst quality (72.4% vs. 63.0%; 62.3% vs. 53.2%). However, these differences were not significant. When stratified by biopsy day and blastocyst quality, a similar trend was noted for good and poor quality embryos. Fair quality Day 5 embryos and good quality Day 6 embryos had equivalent IR and OPR (RR 0.97 95%CI 0.78, 1.20; RR 0.94 95%CI 0.75, 1.17). The IR of poor quality day 5 blastocysts was significantly increased compared with that of poor quality day 6 blastocysts (72.7% vs. 36.0%; RR 0.69 95%CI 0.53, 0.88). Although statistically not significant, the approximate 10% increase in IR and OPR between embryos biopsied on day 5 vs. day 6 is clinically significant and is useful for patient counseling. When the choice is available, a euploid embryo that was biopsied on day 5 should be transferred over one biopsied on day 6, regardless of blastocyst quality.