Babies who never sleep on their stomachs don’t learn behaviors that may lessen their risk of sudden infant death syndrome (SIDS), according to School of Medicine researchers.
Even so, the researchers caution that infants should always be placed on their backs to sleep.
“The first few times babies, who usually sleep on their backs or sides, shift to the prone (lying face down) position, they have a 19-fold increased risk of sudden death,” said senior author Bradley T. Thach, M.D., professor of pediatrics.
“We wondered if these babies, finding themselves face down, fail to turn their heads to breathe easier. If so, is that because their reflexes haven’t developed far enough or because they just don’t wake up?”
Thach and his colleagues studied 38 healthy infants from 3 to 37 weeks. Half of the babies usually slept prone or had a history of turning prone during sleep. The other babies had never slept prone.
The study was reported in the December issue of the journal Pediatrics.
The researchers constructed a moderately asphyxiating surface that caused the babies to re-breathe air they exhaled. This air can have high amounts of carbon dioxide. A catheter taped beneath the babies’ noses allowed monitoring of carbon dioxide levels.
After four to five minutes of sleeping face down on the surface all 38 babies awoke and attempted to get fresher air. The babies with experience sleeping prone generally lifted and turned their heads to either side to increase their supply of oxygen-rich air.
In contrast, the inexperienced infants simply nuzzled the bedding or briefly lifted their heads and then resumed sleeping face down. These babies breathed air high in carbon dioxide.
Overall, infants inexperienced with sleeping prone spent more time fully face down than babies with tummy-sleeping experience.
The researchers suggested that babies learn through experience which head movements decrease the discomfort associated with breathing high carbon dioxide levels.
Therefore, babies with experience sleeping prone are better able to avoid conditions that may trigger SIDS. The research results support the hypothesis, advanced by others, that SIDS may result from insufficiently learned airway protective responses.
The findings also indicate that good head-lifting ability while lying prone may not be sufficient to protect a baby from SIDS.
“Many parents think that if babies can lift their heads, they are okay to sleep prone, but that is a false assurance,” Thach said.
“Parents and other caregivers should never place infants in the prone position until they show the ability to spontaneously turn all the way over.”