On some occasions even if the basic karyotype is normal (46 XY for a man, 46 XX for a woman), closer inspection of the Y chromosome (using advanced genetic technology) may show that there are sections missing – called Y-microdeletions.

If this is the case, and depending on the type of deletion, it may be that there are no recoverable sperm to use for any future IVF treatment, or there may be a small amount that can be used with IVF-ICSI once sperm is retrieved via a surgical procedure called a microTESE. In such cases, any male children will also carry this Y-microdeletion.