Single stranded fragmentation produces different problems than double stranded fragmentation. While single stranded breaks are related to male sterility, double stranded breaks are related to a higher risk of abortion.
Single stranded fragmentation is mainly caused by oxidative stress (tobacco, alcohol...), and is a much more extensive error, affecting a large part of the spermatozoid DNA. This makes it very difficult to repair by the oocyte and, therefore, not even gestation occurs.
In the case of double-stranded fragmentation, breaks are produced at specific points that are unprotected by an enzyme called nuclease, so the damage is not so extensive and can even be repaired by a young egg. Otherwise, if this fragmentation is not repaired, it will give rise to an embryo with chromosomal alterations that will most probably end in a miscarriage.
Therefore, depending on the problem of the patients, we may find it more interesting to study one or another type of fragmentation. However, the ideal would be to study both types of fragmentation, given that there could be problems in both.