July 6, 2010 -- Car seats are supposed to protect infants from injury during a traffic accident, but they can increase the risk for injury when used inappropriately outside of the car, such as in the home or in a shopping cart, according to a new study.

Shital N. Parikh, MD, an orthopaedic surgeon at Cincinnati Children’s Hospital Medical Center, led a study analyzing data from the Consumer Product Safety Commission’s National Electronic Surveillance System database. The researchers estimate a total of 43,562 car seat-related injuries resulted in trips to the emergency room between 2003 and 2007. Injuries that occurred during a traffic accident were excluded from the analysis, and only infants 1 year old and younger were included.

The researchers found that based on a sample of nearly 1,900 infants:

85% of injuries were related to falls. Of these, 64.8% fell out of a car seat; 14.6% of injuries were caused by a car seat falling from an elevated surface; and 5.6% occurred from other types of falls.

Head and neck injuries were the most common type of injury; 84.3% of infants suffered a head or neck injury, 62.4% of which occurred in infants younger than 4 months old.

54.4% of injuries occurred in baby boys.

8.4% of infants had to be admitted to the hospital for their injuries.

Three deaths occurred.

Researchers also reported that the most common surfaces from which infants fell out of car seats included shopping carts (8.1%), tabletops (6.3%), and countertops (3.8%). The study is published in the August issue of Pediatrics.

Car seats have reduced traffic-related fatalities by 71%, the authors note. However, parents need to be educated about the risks of improperly using car seats in the home, they say.

Overall, “injuries are a leading cause of death and morbidity for the first year of life,” the authors write. In this sample, newborns to babies aged 4 months appear to be particularly vulnerable to car seat-related injuries in the home. Younger infants spend more time lying down compared with older infants, who are more mobile. “This fact could give parents a false sense of security,” the researchers write.