Sperm DNA fragmentation (SDF) refers to breaks or damage in the DNA strands within sperm cells. It is measured using tests such as the sperm chromatin structure assay (SCSA) or the comet assay, and expressed as a DNA fragmentation index (DFI). A DFI above 25-30% is associated with reduced fertilisation rates, poorer embryo development, and higher miscarriage risk. The British Fertility Society recommends SDF testing for men with recurrent miscarriage or repeated IVF failure.
Effect on frozen sperm
Cryopreservation does not repair existing DNA fragmentation, but it does not significantly worsen it in samples with normal baseline SDF. In samples with high pre-freeze SDF, the freeze-thaw process may cause a modest additional increase. Samples are stored in cryovials or straws in semen storage tanks at -195.8°C regardless of SDF result, as banking before cancer treatment takes priority over DFI levels.
Cryolab supplies semen storage tanks and andrology consumables to UK fertility clinics. Visit cryolab.co.uk or call 01243 781 121.
