Not if you are male, anyway. I ran across a Facebook posting which linked to an article in the Israeli newspaper Haaretz. The article warned of a “stark correlation … between heavy cell phone use and male infertility.” Haaretz advises that you never use your phone when it is less than 50 cm from your crotch and, oddly, that you not talk on your phone while it is charging. The second stricture seems to me to be even more mysterious than the first; I suppose the phone gets hot when it is charging, but I do not know anyone who deliberately keeps it in his underpants.
I followed a link from Haaretz to an article, “Habits of cell phone usage and sperm quality – does it [sic] warrant attention?” You can read the abstract here; the full article will cost you $35.95 (US). The study is evidently based on questionnaires submitted by 106 nonsmoking men who had been referred to an infertility clinic for semen analysis (26 of the submitted questionnaires were rejected, according to Haaretz). I do not know whether there was a control group, and I have no intention of spending $36 to find out.
My advice to all men who plan to someday have children: Keep your phone away from your pants and, while you are at it, not too close to your brain.