However, there wouldn't be any place to hide on a spacecraft if the wife got really mad at you. How many couples could go two years without an argument? I can see it now, "Well, if he thinks I look fat in this space suit, let's see what happens the next time he goes outside the airlock!"

Seriously, if they did send a mixed crew, I'd suggest they consider sterilization before the flight. We're a very long way from safely having a woman conceive in microgravity and carry a baby to term. Not only are there the possible effects on skeletal-muscular development to consider, there's the higher background radiation that could cause defects.