Babies who spend too much time lying on their backs can develop deformational plagiocephaly, or flat-head syndrome, a flattening of the back of an infant's skull. A study in the journal Pediatrics found that 25 percent of babies with flat-head syndrome had less-developed motor skills, but pediatrician Dr. Jim Sears explains that the delays were mild and temporary.
"It's important to know that it's not the flat head compressing the brain and causing the delays," Dr. Sears says. "It's simply the fact that the babies are probably a little less stimulated because they're lying there ... in the same direction all the time."
Dr. Sears assures that the shape of a baby's skull will even out once he or she is able to sit up unassisted and can sleep in varrying positions. To prevent flat-head syndrome, Dr. Sears recommends shifting a baby's position in a car seat frequently, especially if he or she tends to sleep on one side. You can place a baby on his or her belly if he or she is awake and under adult supervision.
"You don't want the young babies to sleep on their bellies, because then you increase the risk of [sudden infant death syndrome]," Dr. Sears says.