[The quality of conceptus as a function of father's age].

Testicular ageing affects at the same time the individual and his lineage. In the individual, vascular, endocrine, blood testis barrier and Sertoli cells changes because of age lead a decrease of spermatozoa number and an alteration in their form and motility. These changes lead a gradual decrease of fertility. In the progeny, paternal ageing is responsible for new dominant autosomic mutations which themselves cause different malformations and perhaps for certain chromosome X linked recessive mutations. Moreover, in animal and man, paternal ageing seems responsible for a gradual lowering in the level of progeny cerebral functions. In man, very youthful age was also related to these effects. Maternal age did not appear to play a part in this event. On the whole, these results pose the problem of the optimum age for fatherhood.