There has been some concern that the electromagnetic fields emitted by cell phones could lead to sperm damage and male infertility. However, cell phones do not emit enough energy to mechanistically cause damage to sperm. For this reason, the World Health Organization recommends no further research initiatives on this topic.
A recent publication in Environmental International reviewed several articles on the topic. The design of the studies included in the article varied widely and in many cases were not blinded, thus potentially leading to bias. The study did not provide meaningful information that would warrant a change in the previous conclusions on the safety of carrying cell phones in pant pockets.
Stress and potential distraction from intimacy caused by cell phones continues to be the greater concern for fertility. Cell phones remain a part of our everyday landscape, but are probably best left in the off position when trying to turn things on during baby making.