Parents, here's one thing Drs. Spock and Brazalton can't help you with: your hormones.
Sex hormones fluctuate dramatically in male and female animals in association with childbirth, and often mark the onset of parenting behaviors such as nest building, grooming, and nursing. But the hormonal changes in humans-and their role in parenting-are not as neatly packaged, nor as easily tested.
Two psychologists working separately are making hormonal headway. Alison Fleming, Ph.D., and David Gubernick, Ph.D., find that hormones interact with psychological factors to influence the way-or even whether-parents care for their young.
In a recent study, Fleming, of the University of Toronto, interviewed 29 first-time moms before and after birth to determine how they felt toward their babies. She also measured their levels of estrogen, progesterone, testosterone, and the stress hormone cortisol.
Though levels of all four hormones dropped significantly after birth, none except cortisol correlated in any way with mother-infant interactions. Women who had the highest cortisol and positive maternal attitudes were more likely to smell, touch, snuggle, and play with their baby while nursing than those who did not. Those with a negative maternal attitude became less attentive under the influence of cortisol.
Cortisol levels rise during labor and decline over the postpartum weeks. "The hormone may have the effect of intensifying the psychological relationship with the baby," be it good or bad, says Fleming.
Cortisol may elevate mom's state of arousal, accentuating nurturing behavior if she has primarily positive maternal feelings, increasing avoidance if not. Or, high cortisol could, in certain personalities, elevate well-being, intensifying a mother's motivation to respond affectionately to baby. it may also be that after birth, hormones influence a new mom's sensitivity to and perception of her infant's cues. Last, cortisol may affect the ease with which moms acquire and retain maternal experiences.
But moms aren't the only ones whose hormones are affected by a new baby.
For a month before and a month following the birth of their babies, Gubernick, of the University of Wisconsin, took blood samples from nine fathers. In all, testosterone levels plummeted after baby was born.
Because testosterone can fluctuate with stress, number of orgasms, aggressive behavior, and sleep deprivation, Gubernick paid special attention to such matters. Nothing correlated with the hormone dip.
The decrease in testosterone may be a man's response to general changes in his environment, reflecting, say, an altered daily routine after baby is born. Or reduced testosterone could be a specific response to having a new living being in the house.
Either way, the testosterone changes could have a huge payoff. They may facilitate responsiveness to infants. Men report, for example, feeling an "up-welling of wonderfulness" when holding a baby, says Gubernick.
More research will tell how the 'mones of the parents help them respond to the moans of their babes.