Is there a relationship between mitoscore, clinical pregnancy and live birth rate?

Mitochondrial DNA (mtDNA) content as reflected by MitoScore is provided on preimplantation testing for aneuploidy (PGT-A) reports along with ploidy data and embryos are ranked accordingly. This study explores relationships between MitoScore of euploid embryos, pregnancy and live births. Patients undergoing in vitro fertilization (IVF) with PGT-A from January 2021 to June of 2022 were studied by retrospective review of prospectively collected data. Embryos were cultured in the EmbryoScope time lapse incubator from the zygote stage onwards. Blastocysts were graded as follows: maturity (1-early, 2-full, 3-expanded, 4-hatched), inner cell mass (ICM) morphology (1-good, 2-fair, 3-poor/absent) and trophectoderm (TE) grade (1-good, 2-fair, 3-poor/absent). TE biopsy was performed on day 5 or day 6. Associations between MitoScore, blastocyst morphology, clinical pregnancy rate (CPR) and live birth rate (LBR) were evaluated. Data was analyzed using students t-test, Chi square tests, and one way analysis of variance (ANOVA) as appropriate. A p-value of <0.05 was considered to be statistically significant. Embryos from 147 transfer cycles from 125 patients undergoing IVF with PGT were analyzed. All but 4 were single embryo transfer cycles. Amongst these blastocysts, 96 were biopsied on day 5 and 51 on day 6. A significant difference in MitoScore was seen between those biopsied on day 5 vs day 6 (23.6 ± 8.2 vs 31.4 ± 10.5; p<0.001). Blastocysts with high scoring Grade 1 ICMs had lower MitoScores than those with Grade 2 ICMs (24.3 ± 6.7 vs 29.7 ± 14.7, respectively; p<0.01). CPR for euploid day 5 vs day 6 embryos was 70% and 63% respectively, with a LBR/ongoing pregnancy rate of 65% and 51%, respectively (P=NS). CPR and LBR were not associated with biopsy day or specific MitoScore value. However, when transfers were stratified according to MitoScore values above or below 25, analysis revealed an impact to LBR (see table below).Tabled 1Table: Comparison of outcomes with day 5 vs day 6 Euploid blastocysts with MitoScores ≤25 or >25MitoScoreBiopsy Day≤25>25p-valueCPR564% (41/64)81% (25/31)NS670% (7/10)58% (23/40)NSLBR557% (36/63)77% (24/31)NS670% (7/10)44% (17/39)0.038 Open table in a new tab Increasing MitoScores were associated with delayed embryo development to blastocyst. When selecting amongst day 6 frozen euploid blastocysts for transfer, prioritization of embryos with MitoScores less than 25 may be of value to increase chances of a successful delivery.