Car Safety Seats May Cause Breathing Problems for Infants

AUCKLAND, New Zealand, Dec. 8 -- When infants take lengthy naps in child safety seats, the babies may risk life-threatening oxygen desaturation, according to a small study.

Among 43 infants in New Zealand who had a-life threatening event during over 18 month, nine cases were due to oxygen desaturation and secondary central apnea while sleeping in a child safety seat, said Alistair Jan Gunn, M.B., Ch.B., Ph.D., of the University of Auckland, and colleagues, reported online in BMJ.

The researchers prospectively examined all cases referred to the Auckland Cot [crib] Monitoring Service, which follows up on apparently life threatening events that occur to young infants.

All infants had turned blue or pale at least once, and the caregivers thought the child had stopped breathing. Nine were restrained at the time in an appropriate car seat, of which eight were rear-facing and semi-reclining, the researchers said.

Dr. Gunn and colleagues recreated the events by placing the babies in their own car safety seat while awake. In each case, the infants' heads flexed forward, usually with the jaw pressed down on the chest, which caused intercostal recession when they inhaled.

Previous reports have shown increased oxygen desaturation in premature infants who were placed semiupright in a car seat compared with lying down. Some reports have shown mild oxygen desaturation among some full term infants, especially those with pre-existing health conditions.

However, only one of the nine infants in the study was born preterm and the rest had normal growth. Mean birth weight was 9.94 pounds (3,149 g) and the desaturation event occurred at a median age of five weeks (range three days to six months).

None had anatomical abnormalities of the face or upper airway, with normal jaw size and no evidence of laryngomalacia. There were no known medical complications among the term infants.

This highlights that parents should be aware of the possibility of improper head positioning during sleep in a car seat for all children in early infancy, the authors said. The back of the head is relatively large and prominent in infants, which promotes bending, and head control may not be well developed yet. Also, the pharyngeal muscles relax during sleep further promoting flexion.

"Providing a gap behind the head for the occiput allows infants to avoid bending the head, with reduced frequency of episodes of desaturation," the researchers wrote. "Modifying car safety seats so that head flexion is unlikely could avoid the risk of apparently life threatening events."

Also, five of the nine mothers in the study were smokers, "and nicotine exposure could have reduced hypoxic arousal."

The results should not be taken as an indication that car safety seats do not help children, commented Michael Hayes, Ph.D., of the Child Accident Prevention Trust in London.

"They have the potential, when fitted correctly and used consistently, to reduce the severity of injuries and the likelihood of death," he wrote in an editorial. "When used properly, child passenger restraints reduce injury by 90 to 95% for rear facing systems and 60% for forward facing systems compared with not using a restraint."

The American Academy of Pediatrics offers tips for parents in using and fitting car safety seats.

"Premature infants should be observed in their car safety seats while still in the hospital to make sure the reclined position does not cause low heart rate, low oxygen, or breathing problems," it recommends. "If possible, an adult should ride in the back seat next to your baby to watch him closely."

All infants in the study were sent home with breathing monitors and their parents were advised on appropriate positioning and to not leaving the infant for excessive periods in the car seat. No further episodes were reported among the infants during the following year.

The study was supported by a grant from the Turanga Trust. The authors declared no competing interests.