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Why Do Babies Smile in Their Sleep?

The smile of a baby is one of the most heartwarming sights in the world. Just why do babies smile, anyway? 

The first few years of a child’s life are the most formative, setting the stage for adolescence and adulthood. Unlike us, they’re still developing their emotions and personality. The reasons they smile might take you by surprise!

Below you’ll learn about the physical, emotional, and mental state of your infant and what their smiles mean.

Passing Gas

This is no mere fart joke! Babies tend to smile while passing gas. When you consider how sensitive their constitution is, it makes perfect sense. 

Babies are sometimes troubled by upset stomachs, diarrhea, and food that doesn’t go down quite right. When they pass gas, they relieve some of the pressure on their lower abdomen. This is a nice bit of pain relief that results in, you guessed it: a smile.

REM Sleep Cycle

Do babies dream of electric sheep? While science hasn’t quite figured this question out, we do know that babies tend to smile because of their REM cycle.

The REM cycle is an essential part of your physical and mental health. Short for ‘rapid eye movement’, this cycle refers to a state of mind where we experience the deepest and restful sleep. Sleep is proven to repair our body from physical illness, improve our concentration, and boost our immune system.

Next time you see your baby smiling and squirming in your sleep, rest easy knowing they’re having a pleasant dream. White noise can also help a baby fall asleep much more smoothly.

Related: Calming Songs To Sing To Your Baby

Developing Emotions

As we stated above, babies are still developing their emotions. This sentence can sound abstract, but it makes a lot of sense once you think about it.

Babies have to learn how to grab objects and manipulate them, often through play or copying their parents. Babies sometimes mimic what we say or sign to develop language. Emotions are a complex tool that help us navigate the world, relate to people, and understand ourselves.

When a baby smiles, it’s sometimes a sign they’re practicing what it means to feel happy. 

Other Medical Causes

This may come as a surprise, but constant smiling in your baby is sometimes a sign of a deeper medical problem. If your baby keeps smiling or laughing without a discernible cause, they could be experiencing a seizure.

One of the most common types of seizures that affects babies is the ‘gelastic seizure’. You’ll recognize this medical issue from signs such as:

  • Constant laughing
  • Non-stop smiling with no apparent reason
  • Rapid heartbeat
  • Face and skin seem flushed
  • Strange breathing, such as too fast or too shallow

We know how daunting it is to be a new parent. Today we provide mothers of all experience levels practical tools and advice to make the parenting process smoother.

 baby in a pink onesie looking up and laughing

Types of Smiles in Infants

It’s time to sort out baby smiles, even though they all look magical at the end of the day. Learning about your baby’s joy is one of your best tools in communicating with them and helping them grow into a confident adult.

Social Smile

Does your baby smile when they’re around other people? Are they prone to laughing when people play with them or hold them? This smile is a sign they’re becoming social and responsive.


It’s common for adults to encourage social smiles from babies by:


  • Making funny faces
  • Talking normally (no baby noises, you want to help an infant learn language!)
  • Playing a game

Related: When Does Baby’s Hair Grow

Responsive Smile

Your baby should be attentive, curious, and responsive to their environment. If your infant seems disconnected or tired, it could be a sign of a health issue.


Responsive smiles are exactly what they say on the tin: responsive. Babies tend to respond to outside stimuli such as noises, gestures, unusual sights, movement, and soft shapes. Pay close attention to your young one to see what they tend to respond to and what they ignore.

Reflexive Smile

This type of smile is primarily unconscious and is a sign your baby is learning how to move their muscles. Similar to kicking or thumb sucking in the womb, there’s no social or emotional connection.

Most infants will start to show reflexive smiles within days of being born. These smiles will gradually shift to responsive smiles once they reach three months of age. As your child evolves, so too will your understanding of their psychology and emotional growth.

Related: Where Should My Newborn Baby Sleep?

 a baby in a striped hat and shirt holding a shoe and smiling

Conclusion 

Why do babies smile in their sleep? As it stands, there are several reasons. 

Babies usually smile in their sleep because they’re passing gas or enjoying their REM cycle. When babies are awake, they usually move between responsive smiles or social smiles to learn more about their environment. Reflexive smiles are more frequent with newborns and are a sign they’re learning how to use their facial muscles.

The only type of smile you should be concerned about is the gelastic seizure, which manifests as constant smiling, laughing, flushed skin, rapid heartbeat, and erratic breathing.

Learning about your baby’s health is an ongoing journey. Contact us today to learn about our helpful and customizable baby boxes to make your job easier!