That’s according to a review published online in the Journal of Andrology that examined the links between cell phone radiation and your swimmers.

Researchers throughout the U.S. and the world have looked at the impact of your mobile phone’s electromagnetic frequency (EMF) radiation on sperm, and the results—though not yet conclusive—present a compelling case that cell phones damage sperm quality, says the Italian review.

Several studies have shown men who use cell phones have decreased sperm concentration, slower sperm, and damaged sperm, compared to guys who don’t use cell phones. In general, men who use cell phones the most are at the greatest risk.

It’s where you carry your phone that matters, research shows. Just 2 months ago, South African researchers published a study that found men who carried mobile phones on their hip or in their front pants pocket had slower-swimming sperm, and less-concentrated sperm—both of which could cause fertility issues. The amount of sperm abnormalities increased among guys who spent more time tied to their phones.

In another recent study, Turkish researchers subjected human sperm in lab dishes to one hour of cell phone EMF radiation. The exposure caused sperm abnormalities, including sperm that had problems attaching to eggs.

“This should serve as a wake-up call to those men in their reproductive years who keep their cell phones in their pants pockets,” said Joel Moskowitz, Ph.D., director of the University of California, Berkeley’s Center for Family and Community Health.

The results of animal-based experiments are just as worrisome.

One research team placed rats in specially designed Plexiglas cages with a cell phone positioned .2 inches below the bottom of the cage (and the rats’ cojones). After exposing the rats to the cell phones 6 hours a day for 18 weeks, the researchers observed a 25 percent drop in the rats’ percentage of live sperm—from 70 percent to under 45 percent. They also saw sperm “clumping,” a condition where sperm stick together, and so aren’t as likely to fertilize an egg. However, in a 2010 study where rats were exposed to radiation for only 90 minutes a day for 12 weeks, researchers didn’t detect any adverse effects on sperm development.

Despite the bulk of evidence indicating your cell phone may be a pocket rocket pointed squarely at your baby makers, Moskowitz said studies are still deemed “inconclusive” because researchers aren’t yet sure why mobile phones impact sperm.

One theory is that cell phones warm up when in use, and so may increase the temperature in the area around your crotch when stored in your pants pocket, the Italian study says. And your boys don’t respond well to heat: Your testicles hang outside of your body because your sperm needs to stay about 4 degrees cooler in order to survive.

Another hypothesis has to do with the electromagnetic frequency (EMF) emitted by your cell phone. Both cell phones and the cells in your body generate EMFs. Your phone’s high-frequency EMF radiation penetrates deep into your tissue, increasing the random molecular motion inside your body’s cells, studies say. And screwing up your body’s electromagnetic frequency at a cellular level could explain the abnormal sperm, experts posit.

So, what should you do? Take steps to protect yourself and your future selves by never carrying your phone in your pants pocket. For every millimeter you put between yourself and your phone, studies have found you decrease your body’s cell phone radiation absorption by 15 percent. And be aware that smartphones like Blackberries and iPhones may emit more radiation than simpler devices, according to recent research.