University of Iowa researchers say they’ve discovered a genetic abnormality that prevents some men from conceiving children. The findings, which were published this week on the American Journal of Human Genetics website , could one day lead to a birth control pill for men.

Dr. Michael Hildebrand helped lead the study and says the defective gene basically makes sperm unable to swim forcefully enough to penetrate the egg. "In these particular patients that have this defective gene, without the protein they need, these sperm can swim to the egg but they can’t make it into the egg and fertilization doesn’t take place," Hildebrand said.

Researchers now hope to find and study more men that carry the defective gene. Hildebrand says the next steps would involve finding ways to correct the gene that causes infertility and then potentially develop a male contraceptive. Currently, the only contraceptives available for men are condoms or a vasectomy. Hildebrand says a great deal of research is still needed, so it could be some time before a birth control pill for men hits the market.

"Probably somewhere in the range of five years," Hildebrand said. "Initially, studies would have to be done in animal models to show that a particular drug was effective in actually reducing fertility and that it was actually safe. Following the animal studies, we’d have to do clinical trials in human patients."

Hildebrand says he’s confident that any treatment could also be reversed. Researchers have been working for years to develop a male birth control pill, but those studies have generally focused on hormones and sperm production, rather than genetic traits.