Dear Healthy Men: My wife and I are planning to start a family and her doctor suggested that she start taking prenatal vitamins to prepare her body for pregnancy. When I asked the doctor whether there was anything I should be doing to increase the chances of a healthy pregnancy and baby, she just laughed — which I thought was really insulting. I find it hard to believe that as someone who’s going to be contributing 50% of the genes to our new baby, what I eat and do before the pregnancy is irrelevant. Am I wrong? A: You’re right — on several counts. First, it sounds like your wife’s doctor was…