(CBS) Is a new method of male birth control on the way? It's not a pill or surgery, but can provide months of pregnancy protection, according to a new study.
What is it? A method that uses ultrasound to zaps male's sperm. And it might give men the first new birth control option since condoms and vasectomy were introduced more than 100 years ago, the study authors said.
Ultrasound's potential as a male contraceptive began more than 40 years ago when Dr. Mostafa Fahim of the University of Missouri, Columbia tested it on rats, cats, dogs, monkeys - and even eight men - beginning in 1975. But doctors had tried and failed to replicate Fahim's findings, even when turning up the ultrasound so high that it caused skin burns.
Cut to almost 40 years later, researchers created new technology to retest ultrasound as a viable method for birth control.
For the study, researchers at the University of North Carolina zapped male rats' testes with high frequency ultrasound, and found that by zapping the rats for 15-minute sessions spaced two days apart, the researchers got the rats' sperm count index to zero.
"Unlike humans, rats remain fertile even with extremely low sperm counts," study author Dr. James Tsuruta, assistant professor of pediatrics at UNC Chapel Hill, said in a written statement. "However, our non-invasive ultrasound treatment reduced sperm reserves in rats far below levels normally seen in fertile men." Low sperm count in men is defined as less than 15 million sperm per milliliter, according to the World Health Organization, and 95 percent of fertile men have more than 39 million sperm per milliliter in their ejaculate. The ultrasound got the rats' sperm counts below 3 million, which suggests major pregnancy protection if it works in humans.
The study is published in the Jan. 29 issue of Reproductive Biology and Endocrinology. Tsuruta said more research is needed to determine how long the contraceptive effect lasts, whether it can be reversed, or whether it's safe to use multiple times.
"It's a nice idea, but a lot more work is needed," Dr. Allan Pacey, senior lecturer in andrology at the University of Sheffield in the U.K., told BBC News. Pacey wants to know more about what happens when sperm production increases again for those who decide to have children.
He said, "The last thing we want is a lingering damage to sperm."