Researchers find troubling link between low birth weight and autism
Low birth weight babies, infants born weighing between one and five pounds, can face a host of long-term health and developmental issues, including illness, infection and, according to a study from the School of Nursing, an increased risk for autism.
For 25 years, Jennifer Pinto-Martin, the Viola MacInnes/Independence Professor of Nursing at Penn Nursing, has been involved in a longitudinal study examining a cohort of infants with a low birth weight.
Pinto-Martin, also director of the Center for Autism and Developmental Disabilities Research and Epidemiology, says medical professionals knew very little in the 1980s about the long-term consequences of prematurity. To determine the lasting effects of being born at low birth weight, the cohort was assessed at ages 2, 6, 9, 16 and 21.
Of the 1,105 babies in the study, about 800 survived and were tracked by Pinto-Martin and colleagues. She says they began to realize that a few of the low birth weight babies in their cohort had already been diagnosed with autism, so they decided to take a more systematic look at the population.
When the cohort reached age 16, the teenagers were evaluated and screened for autism. Pinto-Martin says 18 percent screened positive.
With funding from the National Institutes of Health, Pinto-Martin and colleagues then performed a diagnostic assessment of the low birth weight cohort for autism.
At age 21, the cohort was given a full-scale diagnostic assessment comparing those who screened positive at age 16 and those who screened negative to determine the overall diagnostic prevalence. Pinto-Martin says they found a prevalence of 5 percent—five times that of the general population.
“Even though we knew that there were more [diagnoses of autism] in this cohort, we were surprised by the magnitude of it,” says Pinto-Martin. “We thought that it would maybe be double what we see in the general population. The fact that it was five times as much was quite shocking.”
Even more critical, she says, was the smaller the baby, the higher the risk. The autism risk for babies weighing about three pounds is 11 percent.
Pinto-Martin says her research team was among the first to link low birth weight and prematurity to an increased risk for autism, and the first to use validated, gold standard, interactive diagnostic instruments.
“It’s not easy to diagnose autism,” she says. It can take hours for a highly trained professional to complete an assessment of a child. A child could screen positive for autism and not have the disorder. He or she could be deaf or have a profound cognitive impairment.
“That’s why the diagnosis is so important,” Pinto-Martin says. “Eighteen percent screened positive; 18 percent do not have autism; 5 percent have autism, so we need to be careful about that.”
Developmental concerns, says Pinto-Martin, are often pushed aside in pediatric primary care because of time constraints. Nurses, she says, can serve as the “development advocate,” the person in the pediatric office that can focus on a child’s development.
We thought that [diagnoses of autism] would maybe be double what we see in the general population. The fact that it was five times as much was quite shocking.”
“The nurse spends more time with the child than the physician does,” she says. “Nurses have an opportunity to assess development and to talk to the parent about it. At Penn Nursing, we are working to develop a cadre of nurses who can help to identify children with autism through careful screening and diagnosis.” Penn Nursing now offers a post-master’s certificate program in autism.
Pinto-Martin says a mother’s risk of having a low birth weight baby is much greater if she does not care for herself or receive adequate prenatal care. To expecting parents, Pinto-Martin advises, “If you have a baby who’s born prematurely, you’re that child’s best advocate and you know that child better than anybody else.”
If a parent thinks his or her child is not developing normally, he or she should push for an evaluation.
“It never hurts to follow your instinct,” she says. “If you wait, it’s worse for the child. We know for all of these developmental problems, the earlier they’re identified, the better the child does, and that’s very true for autism.”