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Ultrasound one step closer to killing sperm--and the vasectomy

Researchers find that a non-invasive ultrasound treatment dramatically reduces the sperm count of rats, but aren't sure if it's reversible.

Male birth control hasn't progressed since condoms and vasectomies were devised more than 100 years ago. And while the idea of using therapeutic ultrasound to zap sperm has been kicked around for decades, it has never been sufficiently reliable for contraception.

The ultrasound device used on rats. Mettler Electronics

Until now.

Researchers have now found that a commercially available therapeutic ultrasound generator and transducer can significantly deplete the sperm count of rats. The team, based out of the University of North Carolina, relied on funding from the Parsemus Foundation and the Bill & Melinda Gates Foundation.

The results are notable because they improve on the only promising results to date, which came out of the University of Missouri in the 1970s. Other researchers, however, were unable to duplicate those results, which subsequently fell into disrepute.

The North Carolina researchers found that little tweaks to the initial study led them to effectively zap a large percentage of the rats' sperm. They used a very specific temperature (98.6 degrees Fahrenheit, or about a degree lower than the rat's ideal body temperature--thus further demonstrating the importance of low-hanging testicles in sperm preservation) at the very specific duration of 15 minutes for two consecutive days.

Therapeutic ultrasound differs from diagnostic ultrasound in that it uses heat to increase blood circulation in an injured area. And heat, be it from laptops, hot tubs, or tight underwear that keep testes close to the body, has long been understood to be detrimental to sperm. The researchers say they wanted to investigate therapeutic ultrasound precisely because this application of heat is both non-invasive and readily available.

While the researchers call this use of ultrasound "a promising candidate for a male contraceptive" in the Jan. 29 issue of Reproductive Biology and Endocrinology, they add that it must be studied further to not only confirm efficacy in humans but also to determine whether the "therapy" is reversible and what, if any, long-term effects it may cause.

Unfortunately for the researchers finally making a breakthrough, funding has run out from both the Parsemus and Gates foundations.

Meanwhile, an independent researcher by the name of Chris Jenkins decided to take his fertility into his own hands in 1998 by modifying his underwear to keep his testicles closer to his body and thus warmer. He carefully tracked his sperm count over the years, posting the results to his website,

Thirteen years later, in 2011, Jenkins reported that while this long-term modification resulted in no pregnancies with his wife, it does not appear to be totally reversible; since he has stopped wearing the underwear, his sperm count has climbed back up toward normal levels, but the sperm are no longer swimming.

While Jenkins warns on his website that his method is still experimental and should only be used by partners who can "afford to have the method fail," he concludes that the method is "drastically underused."