Part of the show Science of Sex, Smell and Pheromones...
When a woman gets pregnant, why do some men suffer false pregnancies?
I've seen this once with a man who had funny stretch marks on his stomach. His wife was pregnant, and it seems he was showing sympathetic changes with the female body. We know women can affect other women, but the evidence that women can change men's behaviour is a bit controversial. It's certainly possible that the hormonal changes will affect the man, but we don't know if men can pick up the chemicals. Men and women are very different, so it's hard to see how such effects can happen. The answer is no-one really knows!