A high sperm DNA fragmentation index (DFI) influences human reproduction and is observed in infertile men. However, the influence of DFI on unexplained recurrent spontaneous abortion (RSA) remains controversial.

We explored the influence of DFI on unexplained recurrent spontaneous abortion.

We conducted a meta-analysis of DFI (assessed by sperm chromatin structure assay(SCSA), terminal deoxynucleotidyl transferase-mediated deoxyuridine (TdT)triphosphate (dUTP) nick end labeling assay(TUNEL), sperm chromatin dispersion(SCD), single cell gel electrophoresis assay(COMET assay), and acridine orange test(AOT) with unexplained RSA from the Cochrane Library, EMBASE, Pubmed and Web of Science database.

Records were screened for eligible studies and data were extracted to an online data extraction form. The main outcome was the sperm DFI. Summary measures were reported as the mean difference(MD) and Odds Ratio(OR) with 95 % confifidence interval (CI).

We identified 27 articles including 3, 2, 9, 9, and 8 studies using AO, COMET, SCSA, SCD and TUNEL respectively; 7 articles used qualitative methods and 21 articles used in quantitative methods. The combined MD estimates of 7 SCSA studies (MD=5.4; 95 % CI: 1.76–9.03; P<0.01), 9 SCD studies (MD=11.16; 95 % CI:6.70–15.62; P<0.01), and 8 TUNEL studies (MD=12.12; 95 % CI: 3.34–20.91; P<0.01) showed significant differences. Notably, qualitative studies showed consistent results with quantitative studies.

These findings support an association between sperm DFI and recurrent pregnancy loss. Previous studies revealed that DFI negatively impacts unexplained RSA.