Limit newborns' time in car seats to travel, study suggests

The study, conducted in Slovenia, measured oxygen levels in 200 healthy newborns when they were in a hospital crib for 30 minutes, then a car seat for 60 minutes, and then a car bed for 60 minutes. Half of the babies were in the car bed before the car seat. The researchers chose Slovenia because newborns stay in the hospital much longer than in the United States, Kinane said, making it less disruptive to ask parents for that much time with their infants.

All the babies had lower oxygen levels in the car seats or car beds than when they were in cribs, and about one in five babies had levels as low as what occurs as a result of prolonged obstructive sleep apnea, Kinane said, a problem that has been linked to slower learning in older children. About 20 percent of the babies had these lower oxygen levels while in the car seat and about 17 percent had similar levels in the car bed, a safety device used more commonly in countries outside the US.

The babies' oxygen levels were lower in the final 60 minutes of the trial, whether they were first in the car seat or car bed, suggesting that oxygen levels might decline the more time they spent in them.

Both the angle of the babies' heads in the more upright car seats and the weight of the harness and buckle on the babies' chests in both car seat and car bed seem to be at fault, Kinane said, noting earlier studies in premature babies that showed similar results. Even full-term newborns' muscles aren't strong enough to compensate for the extra weight of their heads or the car seat straps on their airways.

"The real issue is how we use [car seats] nowadays," Kinane said. "We take the baby car seat out of car and if the baby is still asleep, people don't want to wake them up."

The study sends an important message about using car seats or beds only as they were intended, Dr. Lucky Jain, a neonatolgist at Children's Healthcare of Atlanta and vice chairman of pediatrics at Emory University School of Medicine said in an interview. But it is important to remember that normal oxygen levels in newborns only one or two days old are not known. Babies do show drops in oxygen saturation levels while they are breast- or bottle feeding, for example.

"Parents should not take this to mean their child is being deprived of oxygen or that this could result in injury to the brain," Jain said. "Transient drops in oxygen saturation are for the most part considered normal. This is not any reason for parents to be alarmed."

Funding for the study came from Aprica, which makes both car seats and car beds. It had no role in the design, conduct, or conclusions of the study, Kinane said.