Oct. 13, 2003 -- Smoking marijuana makes sperm less fertile -- even if the woman is the one who smokes it, a new study shows.

Marijuana-smoking college men volunteered for the study led by Lani J. Burkman, PhD, director of andrology at the University of Buffalo School of Medicine and Biomedical Sciences.

The smokers weren't the only ones who got high. The drug affected their sperm, too. These stoned sperm party hard. And then? They burn out, researchers say.

"Marijuana-smoking men's sperm are hyper. They are way out there," Burkman tells WebMD. "They already have begun the vigorous swimming called hyperactivation. Sperm should be quiet at first. They should be waiting to be washed into cervix and approach the egg before they start hyperactivation."

So the little guys are fast out of the gate, right? What's wrong with a little head start?

"It is not a head start. They are going to blow it," Burkman says. "They're too fast, too early. Each individual sperm can maintain this swimming only so long, only several hours. Then it poops out. If it has run out of hyperactivation before it gets close to the egg, it will not fertilize. These sperm are going to burn out."

Burkman announced the findings at this week's meeting of the American Society of Reproductive Medicine.