Great information ladies! LuvMyBoys... I have also wondered the same thing. Particularly because of my husband's job. He flies jets, so I often wonder how those poor male sperm can survive the tight harness they wear and the stress of the flight. I have heard that there is a study out there showing that jet pilots do have more girls than boys. So, my point is that depending on lifestyle behaviors I think the man's sperm can be affected. Maybe, more female sperm survive all of that, so they have more girls.