Why 'new baby smell' is so addictive

Study explores impact on mothers' brains

There's nothing like "new baby smell"—and researchers suggest that the phenomenon isn't just an olfactory hallucination, but a very real biological trick designed to get parents and children to bond.

Writing in the New York Times, Douglas Quenqua reports on a recent study in Frontiers in Psychology that confirms "eau de newborn" serves as a biological incentive for mother-infant bonding.

For the study, researchers monitored the brain activity of 30 women—15 who had recently given birth, and 15 who had never given birth—when presented with the smell of newborns taken from pajamas. All of the women showed activity in the brain's dopamine pathways that light up during reward-inducing behavior. Mothers who had recently given birth had the strongest reaction to the newborn scent.

Study co-author Johan Lundstrom posits that women's brains are hardwired to incent a mother-child bond, which is critical for newborns' survival. "We think that this is part of a mechanism to focus the mother's attention toward the baby," he says, adding, "When you interact with the baby, you feel rewarded."

But what causes the new baby smell?

The new baby smell itself, like other body odors, is probably the result of several factors, Lundstrom says.

"Odors are chemicals, [but] it's really hard to establish which chemicals. In natural body odor we have roughly 120, 130 individual chemical compounds, and they vary by individuals," he says. Moreover, baby smell is relatively short-lived, disappearing by about six weeks of age, on average.

One likely cause is vernix caseosa, or the white, waxy substance that covers babies at birth, Lundstrom says. Although hospital staff usually wash the substance off after delivery, some traces can remain in the baby's hair or folds of the arms and legs and contribute to new baby smell as it breaks down.

Amniotic fluid also has a distinct scent that could contribute to new baby smell, Quenqua reports. In a 1988 study, researchers asked 15 mothers and 12 fathers to identify which of two bottles of amniotic fluid belonged to their child; 12 of the mothers and 11 of the fathers guessed correctly (Quenqua, "Well," Times, 10/2).


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