"A newborn’s body clock isn’t set yet," says Yale University pediatrics professor Scott Rivkees, M.D., who wrote about baby sleep patterns in the August issue of the American Academy of Pediatrics’s journal, Pediatrics. The reason most of us sleep all night and wake up in the morning is that we have circadian clocks — daily biological rest/activity rhythms that get synchronized to light and dark cycles.
A baby’s circadian clock is fully formed before he’s born, but until he’s 2 to 5 months old, his brain isn’t mature enough to fully respond to it. By then, he’ll sleep more like you do — for at least five to six hours at a time at night.
But you can foster the process. "Expose your baby to normal light and dark cycles," he says. "Just because a newborn developed in the dark environment of the womb doesn’t mean he needs it that way now!" When he wakes up in the morning, feed him in a well-lit room. In the evening, dim the lighting. This will reinforce his circadian clock and help him establish a good daily rhythm. Keep up this pattern through his first few months.