When babies smile in their sleep it's called neonatal smiling or reflex smiles which is a normal reflex that the baby cannot control.
A baby smiling while they are sleeping or sometimes at other times does not always mean the baby is happy or thinking about something happy.
Babies smiles are called “reflex smiles.”
Babies start reflex smiling before birth and continue to do so as newborns.
These smiles happen randomly and reflex smiling usually stops around 2 months after birth, right around the same time you can expect baby's first real smile.
The reason babies sometimes smile in their sleep is Neonatal Smiling which happens from birth to one month of age.
The Neonatal smiles happen during drowsiness or during the stages of REM sleep.
When a baby smiles in their sleep the babies smiles are subcortical in origin and will actually decrease with maturity.
Premature babies actually smile more in their sleep than full term babies do.
It's natural and it's actually cute as well but it soon will stop and you'll actually miss those cute smiles in the babies sleep.
A baby's first social smile usually appears by the end of their second month.
That's one reason why, as a pediatrician, seeing babies and their parents at the 2-month-old checkup is always a great pleasure.
Smiles have been noted in the first few days of life as a response to stroking of the cheek or the belly.
Newborns also smile in response to sweet tastes and smells.
These findings were published decades ago when smiles were considered purely as innate reflexes.
By three weeks, your baby may be trying out their first smile, copying your face movements and poking their tongue
They may even start making sounds other than crying, who'd of thought it?