Mom may be the one carrying the baby, but she's not the only one riding a hormonal rollercoaster for nine months before the little one comes. As women's hormone levels increase as the pregnancy matures, men's may go down, accounting for what used to be thought of as purely sympathetic weight gain.
"There are hormonal changes going on with men as well, and they occur earlier than other studies have suggested," said lead researcher Robin Edelstein, an associate professor of psychology at the University of Michigan, Ann Arbor. "What we found is there is a gradual decline in men's testosterone."
The research team followed and analyzed 29 expectant heterosexual couples who all were expecting their first child. They team studied four different periods throughout the pregnancy including evaluating salivary testosterone, cortisol, estradiol and progesterone. At weeks 12, 20, 28 and 36 the team analyzed the couples’ hormones.
The results showed levels of all four of the hormones increased in women, however, men showed declining levels of testosterone and estradiol. The men showed no changes in levels of cortisol or progesterone.
The researchers did not have a definitive answer for why hormones change in men but they estimate that men with lower testosterone might be better caregivers, as they would be less aggressive.