"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," she
The study was published online Dec. 15 in the American Journal of Human Biology
team followed 29 expectant heterosexual couples, all expecting their first child together.
They looked at four different times throughout the pregnancy, evaluating salivary testosterone, cortisol, estradiol and progesterone.
They looked at the levels of those hormones at weeks 12, 20, 28 and 36.
As expected, levels of all four of the hormones increased in women. (Women's testosterone declines after birth.) Meanwhile, men showed substantial declines in levels of both testosterone and estradiol but showed no changes in levels of cortisol or progesterone.
said few studies have looked at whether men might show hormonal changes as their partner proceeds through pregnancy.
can't explain why the hormones change as they do in men, or what effect that might have.
"That is something we are really interested in," she
"It's something we can look at, but we haven't yet."
One idea, she
said, is that men with lower testosterone might be better caregivers, as they would be less aggressive.
The changes detected, she
said, "are very small," and were not enough to be considered low-testosterone.
The change might be about psychologically preparing to be a father, Edelstein
SOURCES: Robin Edelstein, Ph.D., associate professor, psychology, University of Michigan, Ann Arbor; Tomer Singer, M.D., reproductive endocrinologist, Lenox Hill Hospital, New York City; Dec. 15, 2014, online, American Journal of Human Biology