Babies can absolutely smell, and their sense of smell is one of the most developed senses they have at birth. The olfactory system begins forming remarkably early in pregnancy, with the olfactory bulb (the brain structure responsible for processing smell) appearing around week 9 of gestation. By the time a baby is born, smell is already a primary tool they use to find the breast, recognize their mother, and feel calm.
Smell Develops Before Birth
A baby’s ability to smell doesn’t switch on at birth. It builds gradually throughout pregnancy. The olfactory bulb starts taking shape around 9 weeks of gestation, and its layered structure is in place by 14 weeks. By 28 to 30 weeks, the olfactory bulbs are large enough to be visible on an MRI.
During the final trimester, the fetus is actively breathing in and swallowing amniotic fluid, which carries flavor and scent molecules from the mother’s diet. Garlic, anise, and carrot are among the flavors shown to cross into amniotic fluid at levels detectable by the human nose. This means babies get their first “taste” of their family’s food culture months before they’re born, and those early exposures shape what they prefer after birth. Babies whose mothers ate carrots during pregnancy, for instance, showed greater acceptance and enjoyment of carrot-flavored foods when they started solids.
What Newborns Can Smell
From the very first minutes of life, newborns use smell to orient themselves. When placed skin-to-skin on a mother’s chest immediately after birth, a newborn will crawl toward the breast, guided in part by its scent. Babies placed on a mattress move faster toward a pad scented with their mother’s breast odor than toward an unscented one. When breast odor is held near their nose, they produce more rooting responses and more coordinated arm and leg movements.
At two days old, babies can detect the smell of both amniotic fluid and colostrum, and they treat these two scents as roughly equivalent. This makes biological sense: amniotic fluid and early breast milk share chemical signatures, creating a scent bridge between the womb and the outside world. By day 3 or 4, preferences start to shift. Babies begin orienting more toward breast milk than amniotic fluid, reflecting their rapidly evolving postnatal experience.
Three-day-old newborns can even distinguish their own amniotic fluid from a stranger’s, orienting longer toward the familiar scent. This selectivity shows that prenatal smell memories persist after birth and help babies identify what’s safe and known.
Recognizing Mom by Scent
Breastfed babies learn their mother’s unique scent signature within the first days of life. In one study, 17 out of 20 breastfed infants between 2 and 7 days old turned their heads longer toward a pad carrying their mother’s breast odor than toward a clean pad. This recognition develops through direct contact during feeding, as the baby repeatedly encounters the specific combination of scents on their mother’s skin.
What’s striking is that the attraction to breast odor appears to be partially innate, not just learned. Two-week-old bottle-fed infants who had never breastfed still turned longer toward the breast scent of an unfamiliar lactating woman compared to their familiar formula. When given a choice between the breast odor of a lactating woman and the breast odor of a non-lactating woman, they consistently preferred the lactating scent. Something about the smell of lactation itself is inherently attractive to newborns, regardless of feeding method.
How Smell Soothes Babies
Familiar scents do more than help babies find food. They actively reduce stress and pain. A meta-analysis of seven clinical trials involving 478 newborns found that the smell of breast milk significantly reduced pain responses during medical procedures like blood draws and IV placement. Babies exposed to breast milk odor during these procedures also had better oxygen levels and lower heart rates compared to control groups.
The calming effect extends to stress hormones. Research on preterm infants found that maternal milk odor significantly lowered salivary cortisol levels, the body’s primary stress hormone. Even amniotic fluid odor has a soothing effect: providing the scent of amniotic fluid to term or preterm newborns reduces fussing and crying.
This is why skin-to-skin contact after birth is so emphasized in modern maternity care. The baby isn’t just feeling warmth. They’re surrounded by the familiar scent world they’ve known for months, and that continuity helps them regulate their breathing, heart rate, and stress response during the massive transition from womb to world.
The First Hours Matter
There appears to be a sensitive window in the first hour after birth when scent learning is especially powerful. Newborns exposed to a novel odor for 30 minutes during their first postnatal hour showed a clear preference for that odor two to three days later. Babies who had the same exposure but after 12 hours of age did not develop the same preference. Similarly, four-day-old babies oriented more toward their own mother’s milk (compared to another mother’s) only when they had been in skin-to-skin contact with her right after birth.
Even the process of labor plays a role. Babies born by cesarean section before labor began did not develop preferences for odors they were exposed to after birth in the same way that babies who experienced contractions did. Something about the physiological process of labor seems to prime the brain for scent learning, giving babies born through vaginal delivery or cesarean after labor onset a slight head start in forming smell-based attachments.
Smell as a Developmental Tool
For adults, smell is often background noise. For babies, it’s a primary navigation system. In the first weeks and months, before vision sharpens and before language develops, scent provides critical information: where food is, who is holding them, and whether their environment is safe. Babies use smell to initiate feeding (rooting toward breast odor), to self-soothe (calming in response to familiar scents), and to form their earliest social bonds.
The speed at which these abilities evolve is remarkable. Within 48 hours, a newborn can detect amniotic fluid and colostrum. Within three days, they can distinguish their own amniotic fluid from someone else’s. Within a week, breastfed babies reliably recognize their mother’s unique scent. Each of these milestones builds on the last, driven by a combination of prenatal exposure and rapid postnatal learning. Far from being a minor sense, smell is one of the first and most important ways babies make sense of their world.