Nothing matches the feeling of seeing your baby smile, especially while they’re sleeping. Their little face lights up, and it warms your heart. You might wonder what your baby’s thinking about when they make that smile. And what does it mean?
Most babies under two months old don’t smile socially yet (smiling at someone on purpose). This means that their sleep smiles are, most likely, due to reflexes. That’s OK. Your baby’s smile can still make your heart soar!
In this article, we’ll explore probable reasons why your baby smiles in their sleep. And as you gaze at their sweet smiling face, you can anticipate the joy you’ll feel when they smile directly at you for the first time because you’re you.
Key Takeaways
Table of contents
- Why is REM sleep important for babies?
- Why do babies smile in their sleep?
- Why do babies smile when they’re awake?
Why is REM sleep important for babies?
First things first. REM (rapid eye movement) sleep, which all of us experience, is the most active part of the sleep cycle. During REM sleep, our brain waves speed up, and our eyes move rapidly beneath our closed eyelids.
About 20% of adults’ sleep is spent in REM, and we go through several cycles every time we sleep. For newborns, REM (often called active sleep) accounts for 50% of their sleep, and for older babies, it drops to about 33%.
More is better when it comes to babies and REM! The REM part of sleep is critical for their brain development and growth. Not surprisingly, they spend a lot of time in this active sleep state because they have so much developing and growing to do.
And it really is active! Unlike adults, who stay mostly still during REM sleep, babies move a lot. They twitch, move their limbs, and make sucking motions. And as a small study of babies suggests, they also smile during this part of their sleep cycle.
Why do babies smile in their sleep?
According to the American Academy of Pediatrics (AAP), most babies smile in their sleep before they smile when they’re awake. Their active REM sleep is probably the reason why. But very little research has been conducted to determine why smiling happens in this order.
So babies smile a lot due to REM sleep. But are there more specific reasons why? Most likely, they’re responding to some sort of internal impulse.
Reflexive smile
Babies have many spontaneous reflexes. For instance, the Moro reflex is an involuntary startle reflex. When your baby feels like they’re falling or they hear a loud noise, their arms and legs shoot out, and then they pull them back in.
Reflexes like the Moro reflex are due to the critical, ongoing development of your baby’s nervous system. Your baby smiling in their sleep is a similar kind of reflex.
It may come from an internal biological impulse or brain activity. Regardless of the exact reason why a sleep smile occurs, every time it does, your baby is developing the facial muscles they need for their soon-to-come real-deal smiles!
Mimicking smile
Some newborns can imitate adult facial expressions after just a few days (and some a few hours) of being born. They’re watching us from the get-go!
This kind of mimicry includes smiling. So, your baby may imitate your smile in their sleep to get ready for their first social smile. Again, practicing like this strengthens the facial muscles they need for those future grins.
Developing emotions
Your baby spends their day absorbing positive sensory experiences that inform their social, emotional, physical, and cognitive growth.
During sleep, your baby begins to process the new, exciting experiences they had that day and then they smile! (How could they not?) These smiles are sometimes referred to as endogenous because they represent an internal state of warmth, security, and positive emotions.
Gastrointestinal sensations
Early on, everything is new for your baby. They're taking in sights, sounds, smells, and more for the first time. Physical sensations like digesting and having gas are new, too.
As your baby experiences those feelings in their sleep, they may smile. (Or they may make other, less “happy” facial expressions!)
Note: There’s no medical evidence to prove babies “smile” due to gas, but it’s a possibility we don’t want to rule out.
Gelastic seizure
Most of the time, smiling in their sleep is a perfectly normal and positive part of your baby’s developmental growth. In rare cases, though, smiling and especially laughing during sleep can indicate a gelastic seizure.
Lasting between 20 and 30 seconds, gelastic seizures usually occur when someone is on the brink of sleep. They present as uncontrollable laughter, and they may include squirming, grunting, or lip smacking.
About a third of the people who are diagnosed with gelastic seizures have their first episode when they’re a baby. If you suspect your child is having one, they aren’t in immediate danger, so help them stay calm and safe. Contact their doctor afterward to decide what comes next.
Why do babies smile when they're awake?
Sleep smiles are different from the social smiles your baby will begin to flash at you when they’re between six and eight weeks old. Unlike sleep smiles, which are generally automatic responses to internal cues, social smiles are all about connecting externally.
More specifically, social smiles tend to come from interactions with other people. When you talk to your baby, they may smile in response. Singing or laughing may result in a grin breaking out. Even simple eye contact can result in your baby flashing you a smile.
Once your baby begins getting the hang of this kind of interactive smiling, they intuitively understand that it’s a powerful way to bond. It’s part of their developing social skills, but more importantly, it creates a strong emotional and even physiological response in people.
Sleep smiles don’t nurture this kind of social and emotional growth, but they do lay the critical groundwork your baby will rely on when they finally do socially smile. You can think of the development of their neural pathways and practice moving their facial muscles as a warm-up!
An interesting detail to note: sleep smiles are often closed-mouthed smiles, while social smiles are open-mouthed and feel more genuine.
Give your baby a sleep worth smiling about!
Your baby doesn’t know when they’re smiling in their sleep, but they do know if their sleep environment is something to smile about. And Newton can make sure it is!
From our breathable, washable Crib Mattresses, to our cozy Organic Cotton Sheets, to our wide selection of Cribs themselves, we’ve got everything your baby needs for a comfortable sleep, and everything you need to feel like your baby is safe while they snooze.
Newton’s goal is to give both you and your baby something to smile about!
Frequently asked questions
What’s the difference between my baby’s sleep smiles and wake smiles?
Your baby’s sleep smiles happen during their REM sleep. They can occur at any time, and they tend to be brief. External stimuli have nothing to do with these kinds of smiles.
Between the ages of six and eight weeks, your baby may begin to smile socially. These smiles have everything to do with external stimuli. Your baby may smile in response to you talking, laughing, or singing to them. Eye contact can also create a connection that brings on a smile.
Will my baby outgrow smiling in their sleep?
As your baby gets older, the REM part of their sleep cycle will get shorter. Because this is the time when smiles occur, your baby will probably experience fewer reflexive smiles while they’re sleeping.
That said, many adults smile in their sleep, usually due to dreaming, so you may continue to see it in your baby, too.
Are my baby’s sleep smiles due to dreams that make them happy?
It’s hard to tell if babies dream, and if they do, it’s also hard to know if smiling in their sleep is due to those dreams or not.
Researchers haven’t been able to determine whether or not babies dream. Many feel, though, that because dreams are made up of past experiences, dialogue, and a sense of self, they aren't developed enough to experience them.
