Some English expressions relate to sleeping babies. "Never wake a sleeping baby!" is one of them. Another is "I slept like a baby!" to indicate having had a very restful, deep sleep. The importance of sleep for newborns cannot be overstated, as they can sleep up to 18 hours in a given 24-hour period. Babies have several different states of sleep, from being in a light sleep to a very deep one.
Newborns must wake – or be woken – every 3 to 4 hours in order to eat because their stomachs are so small, although for most babies, they awake on their own to eat. Uninterrupted sleep is essential for a baby to help it grow developmentally as it should.