• Men remain fertile even at an advanced age. 
• Sperm decrease in motility, but not in their fertilizing ability. 
• A man’s age is a risk factor for abnormalities in the baby, especially if the woman is older as well. 

As a man ages, the volume of ejaculate decreases. Likewise, sperm motility is reduced. Por otro lado, el número de espermatozoides producidos y la capacidad fecundante no cambian.

In daily life, we can observe that older men are able to achieve pregnancies with their partners; however, this possibility is lower than that of younger men. The explanation may be the result of several factors, such as lower sexual frequency due to decreased libido, erectile problems, and reduced sperm motility. The latter could also explain why the chances of pregnancy are lower when artificial insemination is performed. On the other hand, when assisted reproductive techniques that do not depend on sperm motility are used—such as In Vitro Fertilization or intracytoplasmic sperm injection—the pregnancy rates for older men are equal to those of younger men. Another concern is whether advanced paternal age increases the risk of babies being born with abnormalities, as occurs with women, but there does not appear to be an increase in anomalies in babies born to older men when their partners are young.

On the other hand, when the woman is over 40 years old, the contribution of an older man to the risk is as significant as that of the woman. The most common anomalies (for example, Down syndrome) can be detected through a blood test of the mother at two months of pregnancy.