Prematurity, Low Birth Weight Increases Autism Risk
About one in every 12 babies in the United States is born with low birthweight, according to the March of Dimes, increasing the risk for serious health problems and lasting disabilities. A new study conducted at the Center for Autism and Developmental Disabilities Research and Epidemiology at Penn Nursing in Philadelphia links low birthweight with a five-time greater likelihood for developing an autism spectrum disorder.
In infants, low birthweight is defined as weighing less than 5 pounds, 8 ounces (2500 grams). There are two main reasons for low birthweight babies – prematurity and fetal growth restriction. Babies born before 37 completed weeks of pregnancy are more likely to weigh less at birth. Factors contributing to full-term babies who are underweight include abnormalities of the uterus or cervix, birth defects, infection, chronic health problems in the mother, and smoking or use of alcohol or illicit drugs during pregnancy.
Dr. Jennifer Pinto-Martin PhD MPH and a team of researchers tracked 862 children born in New Jersey between 1984 and 1987 as part of the Neonatal Brain Hemorrhage Study. All weighed 4.4 pounds (2000 grams) or less at birth. The children were screened for autism at birth, ages 2, 6, and 9. At 16, the adolescents were screened as part of a larger psychiatric follow-up and at 21 diagnostic testing was conducted using the Autism Diagnostic Observation Schedule or the Autism Diagnostic Interview-Revised.
By the end of the study, five percent of the children had developed autism, compared with 1% of the general population over the same time period – prevalence five times higher than expected. And the lower the birthweight, the higher the risk of autism spectrum disorder. Low birthweight and prematurity put children at risk for cognitive and motor disability, note the authors.
"The number of children with a diagnosis of autism is on the rise and [we] haven't been able to explain why," says Dr. Pinto-Martin. "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."
Based on these results, parents of babies weighing less than 2000 grams at birth should have their child screened by a doctor as early as possible. "Developmental screening is often something that is pushed to the side," Dr. Pinto-Martin says. "It's important that we do a really good job of screening every single child." Often, early intervention improves long-term outcome, she concludes.
During pregnancy, a woman can reduce her risk of having a low birthweight baby by participating in regular prenatal checkups, consuming a healthy diet including a prenatal multivitamin containing folic acid, avoiding harmful substances during pregnancy, and managing any chronic health problems that she may have.
Pinto-Martin JA, et al. "Prevalence of autism spectrum disorder in adolescents born weighing March of Dimes, Medical Resources, Low birthweight
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