Preemies with Autism More Likely to Have More Severe Symptoms
Being born prematurely increases the risk of serious health problems and lasting disabilities, including having a greater risk for an autism spectrum disorder. A new study digs deeper to find that preemies born several weeks early also tend to have more severe symptoms and are more likely to self-injure.
Babies born before 37 completed weeks of pregnancy are considered premature. In addition to a greater risk of problems such as hypoglycemia (low blood sugar), breathing problems due to immature lungs, and damage to the brain’s white matter, a premature infant is also more likely to be lower birth-weight than a full-term infant. This additionally increases the risk for health and developmental problems.
Michigan State University researchers analyzed an online database compiled by Kennedy Krieger Institute at Johns Hopkins University consisting of nearly 4,200 mothers with autistic children born between 2006 and 2010. Births were divided into four categories - very preterm (born prior to 34 weeks); preterm (34 to 37 weeks); standard (37 to 42 weeks); and post-term (born after 42 weeks). The mothers completed a pair of questionnaires regarding the symptoms of their children.
Children born outside the standard normal gestational period – either pre-term or post-term – were more likely to have significantly higher screening scores indicating more severe autism symptoms.
Tammy Movsas, a postdoctoral epidemiology fellow in MSU’s College of Human Medicine, says "We think about autism being caused by a combination of genetic and environmental factors. With preterm and post-term babies, there is something underlying that is altering the genetic expression of autism.”
For pre-term births, she says "The outside environment in which a preterm baby continues to mature is very different than the environment that the baby would have experienced in utero. This change in environment may be part of the reason why there is a difference in autistic severity in this set of infants." Very premature infants were specifically noted to show an increase in stereotypical autistic mannerisms.
Movsas added that for post-term babies, the longer exposure to hormones while a baby is in utero, the higher chance of placental malfunction and the increased rate of C-section and instrument-assisted births may play a role.
"The findings point to the fact that although autism has a strong genetic component, something about pregnancy or the perinatal period may affect how autism manifests," said Nigel Paneth, an MSU epidemiologist who worked with Movsas on the paper. "This adds to our earlier finding that prematurity is a major risk factor for autism spectrum disorder and may help us understand if anything can be done during early life to prevent or alleviate autism spectrum disorder."
The Centers for Disease Control and Prevention states that more than half million babies in the United states (one in every 8) are born premature each year. Risk factors for premature birth include chronic health problems such as high blood pressure and diabetes, substance use/abuse (ie: alcohol, smoking and illicit drugs), and problems with the uterus or cervix.
The National Institutes of Health reminds new mothers-to-be that the best way to prevent prematurity are to be in good health before becoming pregnant and to get prenatal care early and often during the length of the pregnancy.
Tammy Z. Movsas, Nigel Paneth. The Effect of Gestational Age on Symptom Severity in Children with Autism Spectrum Disorder. Journal of Autism and Developmental Disorders, 2012; DOI: 10.1007/s10803-012-1501-4