The impact of paternal age on reproductive and neonatal outcomes has always been underestimated, as the focus has been on maternal age, which is much more determinant. However, paternal age has also been negatively related to fertility.
Firstly, age decreases the chances of achieving pregnancy naturally, as the number of spermatozoa decreases after the age of 40, and in addition, the sperm will have a greater fragmentation of their DNA. It is true, however, that these factors will not affect pregnancy rates using techniques such as in vitro fertilisation.
There are also studies that have shown an increased risk of premature births or low birth weight in children born to fathers aged 35 or older, although these findings are not entirely clear. Another aspect is the relationship between paternal age, especially after the age of 50, with a slight increase in the risk of autism and schizophrenia.
Therefore, it could be said that in general the ideal age to be a father would be below 40. From this point onwards, the chances of conceiving naturally start to decrease and there will be an increase, albeit minimal, in the genetic risks for the offspring. However, this does not mean that parenthood is discouraged above this age. Assisted reproduction techniques can compensate for this decrease in fertility and the risks involved will be very low.