Because sperm are so tiny that it makes the DNA they’re carrying very vulnerable to damage from the environment they’re in, and sperm and egg cells are already especially vulnerable to DNA damage as they only have half of what’s normally a pair of chromosomes. Damage to DNA is unavoidable (it’s a daily event) but it’s repaired relatively easily in other cells because the DNA is ‘locked’ together on chromosomes in the strands of a double helix, where each side acts as a ‘template’ to repair the damage with, but the chromosomes in eggs and sperm are a much less stable single strand.
‘DNA fragmentation’ is the term for when parts of DNA on the chromosomes separate, or pieces of them break off, and this can cause the genetic code they carry in cells to become disorganised. Tests for DNA fragmentation have been around since the 1980’s and advances in vitro fertilization (IVF) and intra-cytoplasmic injection (ICSI) techniques have revealed that some DNA fragmentation affects sperm in every sample. However when a sperm that fertilizes an egg has a lot of DNA fragmentation it’s a problem because when cells divide and multiply in a growing embryo everything in them needs to be replicated (especially the genetic material of the DNA), and any problems with the code in the cells will reduce the level of organisation in the embryo, until there comes a point when the viability of the pregnancy is badly compromised.
- The standard semen analysis measures sperm concentration, motility and morphology but it can’t detect DNA fragmentation
- DNA fragmentation doesn’t appear to hugely affect fertilisation or the early stages of embryo development, but becomes more of an issue around implantation time and beyond
- Sperm DNA fragmentation tests detect the percentage of sperm affected and identify men at risk of failing to initiate healthy pregnancies
- Embryos from sperm with high DNA fragmentation have higher risks of implantation failure, miscarriage, abnormalities in the offspring and an increased susceptibility to childhood canceri
- DNA fragmentation levels are closely linked to the success of IUI, IVF and ICSI, and miscarriage ratesii
- Regardless of the type of ART a level of DNA fragmentation above 30% significantly reduces the possibility of successful pregnancy
- DNA fragmentation is much higher in subfertile men, and although high rates are sometimes found in men with normal semen it’s less likely
- There are a number of tests available: the