It’s apparently not just moms who experience hormone changes during pregnancy. Expectant dads may also.
It seems impending fatherhood, or being an expectant dad, can lower two hormones in men–testosterone and estradiol–even before their babies are born, a new University of Michigan study finds.
Previous studies have shown that men’s hormones change once they become fathers. The new U-M study is the first to show that the decline may begin even earlier, during the transition to fatherhood, says Robin Edelstein, the study’s lead author.
“We don’t yet know exactly why men’s hormones are changing,” said Edelstein, U-M associate professor of psychology. “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, fathers’ hormonal changes could have important implications for paternal behavior once their babies are born.”
Expectant mothers experience significant hormone changes throughout the transition to parenthood, but relatively little has been known about the prenatal hormone changes among soon-to-be fathers.
The study, published in the American Journal of Human Biology, examined salivary testosterone, cortisol, estradiol and progesterone in 29 first-time expectant couples between the ages of 18 and 45. The saliva samples were obtained up to four times during the prenatal period at about 12, 20, 28 and 36 weeks of pregnancy.
Women showed large prenatal increases in all four hormones, while expectant dads saw declines in testosterone (which is associated with aggression and parental care) and estradiol (which is associated with caregiving and bonding). No changes were found in men’s cortisol (a stress hormone) or progesterone (which is associated with social closeness and maternal behavior).
So it’s not just about the presence of an infant that lowers testosterone, Edelstein said.
One limitation of the new study–as it relates to lower testosterone–is that researchers do not have a comparison group of men who are not expecting a child.
“Thus, we can’t completely rule out the possibility that the changes are simply due to age or the passage of time,” Edelstein said.