Associations of mitochondrial DNA copy number and deletion rate with early pregnancy loss.

Early pregnancy loss (EPL) is a common event worldwide. Previous studies show that mitochondrial DNA (mtDNA) copy number (CN) is associated with semen parameters and preimplantation embryo viability, indicating the predictive potential of mtDNA CN for ongoing pregnancy outcomes. However, no relevant study has assessed the relationship between mtDNA CN and EPL. Thus, we aimed to determine whether mtDNA CN and mtDNA 4977-bp deletion rate (DR) in chorionic villous tissue are associated with EPL. Chorionic villous tissue total DNA was extracted from 75 EPL cases and 75 healthy controls. Chromosomal analysis was conducted using copy number variation (CNV) sequencing. The mtDNA CN and DR were measured in samples without pathogenic CNVs. The association between mtDNA CN or DR and EPL risk were estimated using logistic regression. The EPL group had a significantly different mtDNA CN (P < 0.001) and DR (P = 0.005) compared to the control group. Both biomarkers were independent risk factors for EPL (CN odds ratio 1.71, 95% confidence interval 1.17 to 2.49, P = 0.005; DR odds ratio 1.07, 95% confidence interval 1.02 to 1.12, P = 0.006). These results suggest that higher mtDNA CN and DR levels are strongly associated with EPL and represent independent risk factors for EPL. Further studies validating these findings and exploring the underlying biological mechanisms are warranted.