Why Do Babies Smile in Their Sleep; What Does It Mean

Why Do Babies Smile in Their Sleep; What Does It Mean

There is nothing more precious and heartwarming than a baby’s smile for new parents. As you are new, you are desperately waiting for the baby’s smile, and one day you are surprised when he/she is smiling during sleep. Your immediate reaction is love and affection for the baby. But you also become curious why do babies smile in their sleep. Does it mean something? 

In this post, we will take a look upon it and help you to understand the reason behind smiling.

Why do babies smile in their sleep

Endogenous smiles occur in newborns and which do not occur in response to external stimuli. Babies sometimes laugh in their sleep due to some specific brain functions as a demonstration of physiological rhythms. A baby’s smile is also a response to dreams. It is impossible to tell the contents of the dream because the babies are not able to express their thoughts. But it is thought that a smile is a response to an incident in the dreams.

Infants use a smile as a tool of communication to express his/her feelings and thoughts. They also smile when they are feeling asleep or awake. It is a reaction which could be a reaction to the pleasurable experience at the time.

How does sleep cause a smile 

To know how babies smile in sleep, you should be aware and understand sleep and its stages. There are two fundamental phases in sleep these are 

  • Non- rapid eye movement(NREM)
  • Rapid eye movement  (REM)

Non- rapid eye movement(NREM)

It is further divided into four phases these are

NREM 1:  The baby starts to feel drowsy, eyes droop, may open and close dozing.

NREM 2: This is when the baby is slightly asleep and will awaken if there is any disturbance

NREM 3: It is the deep sleep stage where the baby is quiet and does not move

NREM 4: It is the most in-depth phase, and the baby continues to stay still unless there’s a loud noise to wake them up.


It is the phase when dreams occur, and eyes move rapidly back and forth. Experts believe that eye movement is due to the dreams which the brain processing. Babies sleep 16 hours a day from half time in the REM phase. So next time, do not be surprised when your baby is smiling while sleeping. It is a good gesture that your baby has a sound sleep with good dreams too.