You know the saying never wake a sleeping baby? Perhaps a partial reason for that is because babies simply look adorable when they are asleep — they are always smiling. Seeing those sweet smiles makes it easy to wonder what they are dreaming about. Their next feeding? Their parents? Or, is this simply just gas? We sat down with Dr. Shelly Senders, founder and CEO of Senders Pediatrics in South Euclid to shed some light on the mystery of the newborn smile.
When smiling starts
Believe it or not, babies actually start learning and practicing how to smile in utero, around 33 weeks. Since they are still continuing to master this reflexive skill after birth, sleep is one of the most common times to see a baby smile during the newborn period. These infant smiles are almost always accompanied by squinted eyes, slow blinks and a slow cooing or gurgling sound.
It is important to make the distinction that unlike reflexive smiles, social smiles (in response to someone or something) tend to come around three months of age. However, both types of smiles indicate normal development for a baby.
They’re in active sleep
Senders says that while adults have four stages of sleep, infants have only three —quiet sleep, indeterminate sleep and active sleep. Active sleep is similar to Rapid Eye Movement (REM) sleep in adults, during which time, most dreams originate. Babies spend about 50 percent of their sleep time in active sleep while adults spend only 20 percent in REM sleep.
“Most smiles occur during this active sleep phase which leads some researchers to believe that they are smiling in response to positive dream imagery,” Senders says.
Unlike REM sleep in adults where the body is paralyzed, during active sleep in a newborn, they will often twitch, make sucking motions and move their limbs, Senders says.
They are practicing using their facial muscles
Researchers believe spontaneous smiles that occur during sleep may help develop the muscles used to smile.
“Smiling may serve as a precursor to complex facial expressions and social skills during daytime,” Senders says. “Infants are remarkably capable of learning.”
Smiling relieves stress on the body
In babies, children and adults, smiling releases the neurochemicals serotonin, dopamine and endorphins, which cause relaxation, lower heart rate and reduce blood pressure.
“Smiling during sleep may serve as a natural painkiller to help deal with the stresses on the body during infant development,” Senders says. “Moreover, serotonin levels in the newborn brain may modulate the infant sleep wake cycle and help the body shift from the in-utero pattern of sleeping more during the day to the desired infant pattern of sleeping more at night.”
