Lessons learned from over 64,000 embryos (day 3 embryos or blastocysts) subjected to PGT-A in the same laboratory: general results, recurrence pattern and analysis of the indications

Research question What is the influence of biological, technical and clinical factors on PGT-A embryo outcomes and what is the recurrence pattern? Design Retrospective study including 64,701 embryos undergoing PGT-A in the same laboratory between 2011 and 2019. Biopsies were performed at the day 3 embryo stage (48.3%) or blastocyst stage (51.7%). Advanced maternal age (AMA) was the main indication (65.6%). Results The aneuploidy rate (AR) was 67.8%, higher in women >35 years than in ≤35 years (71.8% vs 47.4%), and higher in day 3 embryo vs blastocyst biopsies (77.50% vs 58.60%). The trisomy/ monosomy ratio was 1.0 on blastocysts vs 0.8 in day 3 embryos. Trisomy 21 was present in 4.9% of the embryos. In aneuploid embryos, the probability of having ≥1-involved chromosome followed a decreasing exponential pattern. The probability of an embryo being was constant around 30% (40% in blastocysts, 20% in day 3 embryos). The cumulative probability of having ≥1 euploid embryo after 10 biopsied embryos was 95% in blastocysts and 80% in day-3 embryos. AMA was associated with a much higher AR than all other indications, which among them had similar AR and chromosomal involvement. Conclusions There is a considerable decrease in AR from blastocysts to day 3 embryos, which is most notable for monosomies. While AMA shows an increase in AR and a specific chromosomal pattern of involvement, the remaining indications showed a similar AR and chromosomal pattern. Even after producing many consecutive aneuploid embryos, the possibility of obtaining a euploid embryo is not negligible.