Objective: The oocyte is believed to be a major locus of reproductive aging in women. This is manifested by a decline in pregnancy rates among older women undergoing in vitro fertilization (IVF). Consistent with aging, there is an accumulation of mitochondrial DNA (mtDNA) mutations in various non-dividing human tissues (muscle, brain). Such mutations are presumed to arise from intramolecular homologous recombination (HR) during mtDNA replication. It has been suggested that these mtDNA mutations may play a role in oocyte senescence. Many large-scale deletions of human mtDNA have been previously described, the most prevalent of which involves a 4977-bp deletion (ΔmtDNA4977). This deletion results from homologous recombination at 8470–8482bp and 13448–13459bp.