Oct. 17, 2011— -- Children weighing less than 4.4 pounds at birth may be more prone to autism spectrum disorders, a new study suggested.
The estimated prevalence of autism spectrum disorders reached 5 percent in a group of more than 1,100 low birth weight babies, Jennifer A. Pinto-Martin of the University of Pennsylvania in Philadelphia and colleagues found.
That prevalence was five times higher than expected from the general population, the group noted in the November issue of Pediatrics. Indeed, by comparison, the U.S. Centers for Disease Control and Prevention reported a 0.9 percent prevalence among 8-year-olds across the United States in 2006.
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"This prospective study, using rigorous diagnostic procedures, confirms that the rate of autism spectrum disorders is elevated among low birth weight/preterm survivors," the researchers wrote in the paper.
That low birth weight and prematurity put children at risk of cognitive and motor disability has been well established, but their link with autism spectrum disorders was largely through retrospective studies and those that screened without diagnostic confirmation, the group noted.
About 3 percent of children born in the United States weigh between 1.1 and 4.4 pounds at birth.
Pinto-Martin's group studied a population-representative group of 1,105 such infants followed in the Neonatal Brain Hemorrhage Study.
That study was done at three hospitals, which covered 85 percent of low birth weight births, in three central New Jersey counties, from 1984 to 1987. At the time, these three counties were demographically comparable to the nation except for slightly higher incomes and slightly fewer minorities.
Low birth weight tended to be more often linked to autism spectrum disorders in boys than girls (9.9 percent versus 3.3 percent).
The lower the low birth weight, the higher the risk of autism spectrum disorders tended to be, with a 10.6 percent prevalence at less than 3.3 pounds versus 3.7 percent at 3.3 to 4.4 pounds at birth weight.