Why does my baby smile in sleep but wake up crying?

It’s usually normal for babies to smile in their sleep and then wake up crying. Those two behaviors often come from different parts of infant sleep and from the fact that babies are still learning how to settle themselves.

Why babies smile in their sleep

• Active sleep: Babies spend a lot of time in active sleep, when their brains are very active and you may see twitches, eye movements, and facial expressions like smiling.
• Reflexive smiles: In young babies, sleep smiles are often involuntary and not a sign of a dream or emotion.

Why babies wake up crying

• Sleep cycle changes: Babies have shorter sleep cycles than adults and may briefly wake or stir between them. If they can’t resettle on their own, they may cry.
• Normal needs or discomfort: Hunger, gas, a wet diaper, being too hot or cold, teething, or reflux can all wake a baby.
• Startle reflex: In younger infants, a sudden movement or sensation can trigger the Moro/startle reflex and lead to crying. This reflex usually fades over the first few months of life.
• Need for comfort: Babies may cry when they notice a change in position or environment, especially if they fell asleep while being held.

What you can do

• Give your baby a brief moment before rushing in, since some babies resettle on their own.
• Try to keep the sleep environment consistent.
• Check basic needs like feeding, burping, diaper changes, and comfortable clothing.

If the crying is frequent, inconsolable, or happens with fever, vomiting, trouble breathing, poor feeding, or signs of pain, contact your pediatrician.