Your Baby's Senses: Smell

In previous posts, we've shared information about your baby's senses of hearing and taste. As we continue this series on baby's senses, we move on to babies' sense of smell.

Babies’ sense of smell, called “olfaction,” is highly developed at birth. Scientists think a baby’s ability to smell his mother is one of the important ways he learns to recognize her. Newborns spend a lot of time with their eyes closed! Researchers have found that newborns are able to tell the difference between the smell of their mothers and the smell of other women (yes, they really did a study!). Babies’ early exposure to a smell (in the first couple of hours after birth versus more than 12 hours after birth) results in a stronger and longer memory of the smell. This may be because newborn babies learn from their senses best when they have high levels of the hormone norepinephrine and this hormone is high in most babies in the first few hours after they are born.

Babies don’t have ability to know what smells are; they won’t know a flower or diaper by its smell – that takes experience. But, babies are calmed by familiar smells that they associate with good experiences (like a loving touch or breastfeeding). In contrast, babies may turn away from strangers with strong unfamiliar odors, so you might ask Aunt Mildred not to wear too much perfume when she comes to visit!

Because babies are more likely to remember the odors they were exposed to very early in life, they are more likely to be familiar with and calmed by the smell of their own mothers – since she’s right there after birth. These studies do not mean that babies won’t be able to recognize their mothers’ smell if they are not with her in the first hour or two, but it might take longer than those who are physically close to their moms earlier in life. Many studies have shown that babies who are breastfed or given their mothers’ breast milk during a painful procedure (like getting blood taken) are calmer than those who are not. Researchers think that the combination of the smell of their mothers and the sweet taste of the milk helps babies deal with the stress.

Skin-to-skin contact for about an hour immediately after birth increases babies’ recognition of the smell of their moms’ milk at 4 days postpartum. Early skin-to-skin contact has many benefits for mom and baby and many hospitals encourage the practice immediately after birth, during the best time for learning. Dads can make sure that baby is familiar with their smell by cuddling close early and often!

References

1. Winberg J, Porter R. Olfaction and human neonatal behavior: clinical implications. Acta Paediatr 1998; 87: 6-10.
2. Mizuno K et al. Mother-infant skin-to-skin contact after delivery results in early recognition of own mother’s milk odor. Acta Paediatr 2004; 93: 1640-5.
3. Romantshik O et al. Preliminary evidence of a sensitive period for olfactory learning by human newborns. 2007; 96: 372-376.
4. Nishitani S, Miyamura T, Tagawa M, Sumi M, Takase R, Doi H, Moriuchi H, Shinohara K. The calming effect of a maternal breast milk odor on the human newborn infant. Neurosci Res. 2009;63:66-71.
5. Shah PS, Aliwalas LI, Shah V. Breastfeeding or breast milk for procedural pain in neonates. Cochrane Database Syst Rev. 2006;3:CD004950.
6. Delaunay-El Allam M, Marlier L, Schaal B. Learning at the breast: preference formation for an artificial scent and its attraction against the odor of maternal milk. Infant Behav Dev. 2006;29(3):308-21.