Improved pregnancy outcomes from mosaic embryos with lower mtDNA content: a single-center retrospective study

The purpose of this study is to investigate whether the mitochondrial DNA (mtDNA) content can reflect the state of mosaic embryos.The study included 1669 blastocysts derived from 394 PGT-A cycles between January 2018 and December 2020, in which preimplantation genetic testing for aneuploidy was performed and mtDNA content was determined. The standard deviation (SD) of whole genomic sequencing data was calculated for quality control. mtDNA content was measured as the proportion of mtDNA to genomic DNA. 1558 blastocysts with SD values less than 4.0 and mtDNA values less than 0.4% were selected for statistical analysis.The mtDNA content of the PGT mosaic group was significantly higher than that of the PGT normal group (P < 0.001). Twenty-six mosaic embryos were transferred, and the results were as follows: 2 out of 26 had undergone a spontaneous miscarriage, 15 were not pregnant, and 9 resulted in a live birth. There were significant differences in the mtDNA content between the miscarriage/non-pregnancy group and the live birth group (**P < 0.01; ***P < 0.001). There was no mosaic embryo with more than 0.157% mtDNA content found in the live birth group.This study demonstrates that mtDNA analysis has the ability to identify mosaic embryos with high developmental potential. It can be a valuable supplementary index for the selection of mosaic embryos for transfer. Larger studies with a greater sample size will further our understanding of the relationships between metabolic activity and mosaicism.