One of the most important questions for parents of a child with Klinefelter syndrome is whether there is a risk of the condition recurring in their subsequent children. Non-mosaic Klinefelter syndrome is typically a "de novo" chromosomal anomaly, meaning it is not inherited from the parents. Therefore, the presence of non-mosaic Klinefelter syndrome in a previous child does not increase the recurrence risk in subsequent pregnancies beyond the general population risk, as parental carrier status is not expected. However, other risk factors such as advanced parental age should be evaluated in each individual case.
If an individual with Klinefelter syndrome wishes to have children, there may be an increased risk of aneuploidies in their offspring, such as sex chromosome aneuploidies (e.g., XYY syndrome, XXX syndrome) and trisomy 21 (Down syndrome). Nevertheless, scientific studies have shown that in non-mosaic Klinefelter syndrome males, where focal sperm production is present, mature gametes with a normal chromosomal structure can be produced. This finding supports the observation that the vast majority of children born to these individuals are chromosomally normal.