He'd have to be tested. Anything lower than 20,000,000 is considered a "low sperm count". The Average Male carries anywhere between 150,000,000 to 400,000,000 sperm. As long as his count is above 20,000,000 I'd say his chances are still quite well. Out of the millions of sperm that a man can deposit, only several thousand make it into the cervix and out of those, only several hundred to a couple thousand make it into the uterus.
The exact numbers really vary per male and only a doctor can tell you them.
at 1:58 PM on Apr. 13, 2009