Autism in low birth weight babies five times more common: Study

By Dr. Ananya Mandal, MDOct 18 2011

According to a new study, autism is five times more common among babies born premature or with a low birth weight.

Roughly 3% of U.S. newborns fall into the low-weight category used by the researchers (2,000 grams or less). Babies of this size are typically born prematurely, though certain pregnancy complications can also cause low birth weight in full-term babies.

The researchers followed up 862 premature, low-birthweight infants born in New Jersey between October 1984 and July 1989 until they were 21 years old. Their birthweights ranged from 500 grams (1.1 pound) to 2,000 grams (4.4 pounds). Five percent of the children in the study developed autism, compared with 1 percent of those in the general population, the University of Pennsylvania School of Nursing researchers found. The study appears online and in the November issue of Pediatrics.

There has been evidence that links low birthweight and a number of problems with motor and cognitive skills, but this study is the first to show that low-birthweight children are also at increased risk for autism, according to the researchers. “Cognitive problems in these children may mask underlying autism,” wrote lead author Jennifer Pinto-Martin, director of the Pennsylvania Center for Autism and Development Disabilities Research and Epidemiology.

She added in a university news release, “If there is suspicion of autism or a positive screening test for ASD (autism spectrum disorders), parents should seek an evaluation for an ASD. Early intervention improves long-term outcome and can help these children both at school and at home.”

“For years we have known there's a higher risk of delay and some impairments in some domains of development in low-birth-weight babies,” says Diego Chaves-Gnecco, a pediatrician at the Children's Hospital of Pittsburgh who specializes in development and behavior. But it's difficult to attribute autism and other developmental problems to premature birth or low birth weight “because so many factors could be involved,” says Chaves-Gnecco, who was not involved in the study. “All pediatricians and primary care providers” should be doing the type of screening the researchers used throughout the study, Chaves-Gnecco says. “The earlier the diagnosis, the more intensive the services and the better the prognosis is for the child.”

“Although this group is not the first to report a higher prevalence of autism in the low birth weight infant population, they've done a better job than anyone else in confirming the diagnosis with gold standard tools,” said Dr. Karl Kuban, chief of pediatric neurology at Boston Medical Center, who did not participate in the research. “Is it being born early that's leading to the problem, or is it that being born early and having autism share a common risk?” Kuban said. “We don't know.”

“The number of children with a diagnosis of autism is on the rise and [we] haven't been able to explain why,” Pinto-Martin says. “It's partly a function of awareness and better diagnosis, but we do a better job of keeping tiny babies alive and this may be one consequence of that.” An important message of the new study, Pinto-Martin said, is that pediatricians must regularly screen low-birth-weight children.

Authors add that future research will examine possible links between brain hemorrhage (a common complication of premature birth) and autism. This will be done by examining brain ultrasounds of the children taken when they were newborns.