Lower sperm characteristics in 36 brothers of infertile men, compared with 545 controls.

Among the men who volunteered to become semen donors for artificial insemination at the sperm bank of Centre d'Etude et de Conservation du Sperme Humain, Paris-Bicêtre, some were brothers of the infertile men of couples entering the Artificial Insemination with Donor program. Their sperm characteristics, compared with those of other donor candidates, are clearly lower. The difference is significant for count (78.0 versus 102.8, P less than 0.05) and very significant for the percentage of motile spermatozoa (61.5 versus 66.9, P less than 0.01) and for the percentage of normal forms (51.8 versus 62.7, P less than 0.00001). The differences are even more pronounced when the brothers of azoospermic men are considered. The possibility that some cases of infertility could have a genetic origin is discussed.