Among tested embryos, chromosome number abnormalities were found in 38.2% when the sperm DNA fragmentation index was at least 30%, compared with 24.4% when it was below 15%. The association was more pronounced when women were 35 or older or semen parameters were severely abnormal.
What matters for a healthy embryo in IVF? Maternal age and egg quality usually come to mind. The likelihood of an embryo having an abnormal number of chromosomes increases with maternal age. A study from China suggests there is also a reason to consider sperm health.
Researchers from Central South University, the Reproductive & Genetic Hospital of CITIC-Xiangya and collaborating institutions examined assisted reproduction records from 5,637 couples. They published their findings September 16 in Human Reproduction Open.
DNA damage can occur with normal sperm count or motility
A conventional semen analysis measures count, movement and the proportion of normally shaped sperm. An apparently normal sperm cell can still carry damaged DNA. The DNA fragmentation index (DFI) measures the proportion of sperm showing DNA damage, including breaks in the DNA strands. A higher index indicates more damage.
Sperm deliver paternal genetic information at fertilization, so damage may matter for subsequent development. DNA breaks and an abnormal chromosome count are distinct phenomena. The former does not inevitably produce the latter.
The investigators reviewed treatment records from 2016 through 2023. Of 5,637 cycles, 3,948 met the study criteria. For the chromosome analysis, they assessed 3,574 blastocysts from 1,063 cycles that involved preimplantation genetic testing for aneuploidy (PGT-A).
The clearest difference was in the highest DFI group
The researchers compared DFI below 15%, 15% to below 30%, and 30% or higher. The corresponding proportions of tested embryos with abnormal chromosome numbers were 24.42%, 25.78% and 38.19%. The highest and lowest groups differed by about 13.8 percentage points. After adjustment for factors including both partners' ages and semen parameters, the odds of aneuploidy were 1.35 times as high in the highest group.
The middle group did not differ significantly from the lowest. These findings do not support a proportional increase in risk with every small rise in DFI.
Maternal age and severe semen abnormalities
Among women aged 35 or older, the proportion of aneuploid embryos rose from 38.75% with DFI below 15% to 52.02% with DFI at least 30%. The adjusted odds ratio was 1.61. In the group with severely abnormal semen parameters, such as very low count, poor motility or few normally shaped sperm, the corresponding proportions were 18.03% and 36.81%.
These patterns suggest sperm health deserves consideration alongside maternal age. Maternal age remains a major determinant of embryo aneuploidy. This study alone cannot establish a synergistic effect between maternal age and sperm DNA damage.
Fertilization and chromosome status answer different questions
Overall, fertilization and early developmental measures did not differ significantly across DFI groups. Among men younger than 40, however, higher DFI was associated with a lower likelihood of developing a good-quality blastocyst. The investigators suggested that the egg might repair some sperm DNA damage after fertilization. They did not test that mechanism directly. Normal fertilization and early growth cannot guarantee a normal chromosome count.
Would a DFI test help every couple?
A DFI result might provide additional information for some couples, particularly with older maternal age or poor semen parameters. A high value does not establish that pregnancy is impossible. This retrospective, single-center study cannot determine whether sperm DNA damage caused the chromosome abnormalities.
The study also did not demonstrate that DFI testing or changing treatment according to the result improves pregnancy or live-birth rates. Its findings do not support routine antioxidants, specialized sperm selection or PGT-A for every couple.
Source: “High sperm DNA fragmentation is associated with increased embryonic chromosomal abnormality: a retrospective study of 8 years involving 5637 couples undergoing ART.” Human Reproduction Open, published online September 16, 2026, article hoag082. DOI: 10.1093/hropen/hoag082.
Related reading: Does ZyMot improve IUI pregnancy rates with high sperm DNA damage?.
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