Recently, scientists completed one of the most extensive investigations to date of prenatal hormones in first-time expectant couples. Women showed large prenatal increases in salivary testosterone, cortisol, estradiol and progesterone, while men showed significant prenatal declines in testosterone and estradiol, but no detectable changes in cortisol or progesterone.
While the results in women were expected, the results seen in men suggest that impending fatherhood might cause men's hormone levels to change. Additional studies are warranted to understand whether partners' prenatal hormone changes are linked with postpartum behavior and adjustment.
"Other studies have shown that men's hormones change once they become fathers, but our findings suggest that these changes may begin even earlier, during the transition to fatherhood," said Dr. Robin Edelstein, lead author of the American Journal of Human Biology study. "We don't yet know exactly why men's hormones are changing; these changes could be a function of psychological changes that men experience as they prepare to become fathers, changes in their romantic relationships, or even physical changes that men experience along with their pregnant partners."