Prevalence of high DNA fragmentation index in male partners of unexplained infertile couples

The sperm chromatin structure assay (SCSA) parameter DNA fragmentation Index (DFI) is a valuable tool for prediction of fertility in vivo. Clinical data show that a DFI above 30% is associated with very low chance for achieving pregnancy by natural conception or by insemination. Already when DFI is above 20% the chance of natural pregnancy is reduced, this despite normal conventional semen parameters. The aim of the present study was to investigate the prevalence of high DFI in male partners of unexplained infertile couples to further identification of male factors contributing to subfertility. Among 212 consecutive men under infertility investigation, 122 cases with the diagnosis 'unexplained infertility' were identified. For all but three, SCSA data were available. The percentage of couples with diagnosis 'unexplained infertility' in which the male partner has DFI >20% or DFI >30% was calculated. In the group diagnosed with 'unexplained infertility' 17.7% of the men (95% CI 10.8-24.5) presented with 20 ≤DFI <30 and 8.4% (95% CI 3.40-13.4) had DFI ≥30%. A significant part of men diagnosed as unexplained infertile according to traditional diagnostic methods has remarkably high degrees of fragmented sperm DNA. Apart from adding to our understanding of biology of infertility our finding has clinical implications. Couples in which the DFI of the male partner is high can avoid prolonged attempts to become spontaneously pregnant or referral for intrauterine insemination, both having low chances of leading to conception.