Expectant Fathers Experience Hormonal Changes, Too

It's no secret that when a woman is pregnant, all her hormones are out of whack. But a new study shows that expectant fathers experience some hormonal changes, too.

Impending fatherhood can lower two hormones - testosterone and estradiol - even before their babies are born.

"We don't yet know exactly why men's hormones are changing," Robin Edelstein from the University of Michigan, who led the study, said in a statement. "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."

"Nevertheless," she added, "fathers' hormonal changes could have important implications for paternal behavior once their babies are born."

Previous research indicates that men's hormones change once they become fathers, and there is some evidence that this is a function of a decline after the child's birth. But according to the new study, this decline may start even earlier.

To learn more about men and their biological reaction to the happy news of impending fatherhood, Edelstein and her colleagues examined salivary testosterone, cortisol, estradiol and progesterone in 29 first-time expectant couples, aged 18 to 45. They collected saliva samples at about 12, 20, 28 and 36 weeks of pregnancy.

Women reportedly showed large prenatal increases in all four hormones, while men saw declines in testosterone and estradiol. Testosterone is associated with aggression and parental care, while estradiol is linked to caregiving and bonding.

Meanwhile, their levels of cortisol, a stress hormone, and progesterone - which is associated with social closeness and maternal behavior - remained stable.

So this goes to show that having a child alone cannot explain the lowered testosterone levels.

"Thus, we can't completely rule out the possibility that the changes are simply due to age or the passage of time," Edelstein added.

The results are described in more detail in the American Journal of Human Biology.

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