In most men, there is a gene that codes for a protein that covers the surface of sperm, allowing them to swim towards an available egg. In some men, however, a genetic variation has turned off the coding for this protein, which, simply put, means that their little guys just can't get anywhere important.

Says MSNBC: "When the gene is mutated, the protein is missing, and the sperm have that problem in transit ... Wives of men with the genetic variation were less likely to become pregnant than other couples and 30 percent less likely to give birth," the researchers said."

Luckily, hope is not lost. Doctors can test for this condition, and if it turns out that the man in your life has it, the handicap can usually be overcome in a fertility lab by placing sperm directly next to an egg or even injecting a single sperm into a ovum in an IVF process.

 

Are you having trouble conceiving? You're not alone. According to Jezebel, an estimated 15 percent of couples have difficulty becoming pregnant - and it's not always the woman's fault. In fact, in many cases, a genetic mutation that makes mens' sperm unable to be properly motile might be the culprit in a significant number of cases, say researchers at the University of California at Davis.