Rate of mosaicism in 21,212 PGS embryos is < 5% by next generation sequencing (NGS)

The objective of the study was to determine the rate of embryonic mosaicism in 21,212 clinical PGS cases utilizing trophectoderm biopsy and NGS. Retrospective. A retrospective review was conducted of all embryos that underwent PGS by NGS over a 27 month period ending in April of 2018 by a large genetics reference laboratory. All patients underwent standard in vitro fertilization (IVF) and preimplantation genetics screening (PGS). All embryo biopsies were performed at the blastocyst stage. 69% (14,636) of the embryo biopsies were performed on day 5 of development and 31% (6,576) of the embryo biopsies were performed on day 6 of development. Next generation sequencing (NGS) was performed on 50ng of DNA from each TE sample. First, the sample underwent enzymatic shearing, fragment stabilization and size selection. Then, sequencing primers and polymerase were added, the samples were loaded onto a sequencing cartridge and analyzed at a depth of 1X across the genome. Amniotic cells underwent routine G-banded karyotyping and NGS sequencing for chromosomes as described above. Forensic testing was performed by DNA profiling uses repetitive short tandem repeat sequences (STRs) and NGS. Different tissues were analyzed for mosaicism. 21,212 clinical PGS cases utilizing trophectoderm biopsy and NGS were identified. Of all samples, 763 (3.6%)mosaic embryos were identified. 29,449 (96.4%) non-mosaic embryos were identified. Utilizing a robust data set, this data suggests that the rate of embryonic mosaicism resulted using NGS is under 5%. Our validation studies on single cells dilutions (previously published) demonstrates the ability of our testing platform to determine mosaicism at the ∼ 10% level. While still clinically significant, this rate of mosaicism is relatively low and this is consistent with our previous reported findings.