Breast milk

Oh also to add, babies don’t quite have a circadian rhythm yet - that is they don’t have fixed sleep cycles. Because they CAN sometimes forget to breathe, they have lighter sleep rather than deep sleep patterns. Often when baby is sleeping you’ll see some rapid eye movement under their closed eyelids. Not going into a deep sleep also prevents SIDS. This is why they only sleep for short hours and take quick naps through the 24 hour day. You can help settle them into a rhythm by making sure the house is brightly lit and there’s lots of noise in the day and darkening and quietening the house in the evening to help baby along.