The male factor
Having a standard semen analysis, in terms of quantity, morphology and mobility does not guarantee that semen is fertile.
There are cases where the “genetic load” (DNA) of sperm is alterated, resulting in fertilization failure or non-viable embryos. This is what is known as sperm DNA fragmentation and depending on the percentage of sperm fragmentation could result in a poorer prognosis of male fertility.
The assessment of DNA fragmentation takes place in the andrology laboratory on a sperm sample by applying a specific technique known as the TUNEL Assay.
The cases where a disorder is diagnosed can be treated with antioxidant drugs. In patients who do not experience an improvement with this treatment, the recommendation for IVF would be to directly obtain sperm from the testicle by PESA/MESA, as a high percentage of fragmentation occurs during ejaculation.
The sperm, like the egg, contributes half of the 46 chromosomes of the embryo that contain all the genetic makeup of an individual.
The cellular process in determining the genetic load in the sperm is called meiosis. It is believed that alterations in meiosis are present already at birth so there is no treatment to correct them.
The diagnosis of abnormalities in meiosis is through a low testicular biopsy, usually performed on an outpatient basis under local anesthetic.