If a man smokes a lot of weed,and possibly has done other drugs in the past.
It does not affect his sperm count what-so-ever. That is a myth. A man who uses marijuana daily - may have a lower sperm count, but it does not disapeer compeltely. Also, once he quits smoking, his sperm count goes back up to normal.
alcohol and drug abuse in both males and females can cause them to be less fertile and even infertile