CHICAGO – Autism is more common in children who had jaundice at birth, a big Danish study found, but researchers cautioned they don't know how the two conditions might be related and that new parents shouldn't be alarmed.
Mild jaundice is fairly common and generally harmless. Severe, untreated jaundice is known to cause brain damage, but it's also rare and hasn't been proven to cause autism. It's possible that children genetically predisposed to autism might also be more vulnerable than others to jaundice.
But if autism and jaundice are related, the study doesn't answer whether one of the ailments might have caused the other, said Rikke Damkjaer Maimburg, the lead author and a researcher at Denmark's Aarhus University.
Maimburg and colleagues examined medical data on all 733,826 children born in Denmark between 1994 and 2004. The results were prepared for release online Monday in Pediatrics.
More than 35,000 newborns had jaundice, while autism was eventually diagnosed in 577 children. Among autistic children, almost 9 percent had jaundice as newborns, compared with 3 percent of other children.
Previous studies on a possible autism-jaundice link have produced conflicting results.
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The new results shouldn't scare parents whose newborns are jaundiced, said Dr. Thomas Newman, a pediatrician and epidemiologist at the University of California at San Francisco who studied the same topic and found no link.
Mild jaundice can cause a yellowish-orange tinge to the skin and simply signals that newborns' livers aren't fully mature. Newborns are typically examined for jaundice before leaving the hospital, and it usually disappears within a week or two without treatment.
"Jaundice is almost always harmless," Newman said. "The evidence for an association (with autism) is weak and inconsistent and evidence for causality nonexistent."
The study lacked data on severity of jaundice, which involves having elevated levels of bilirubin in the body. Bilirubin is yellowish pigment created as the body recycles old red blood cells. It is processed by the liver; during pregnancy the mother's liver handles the job and sometimes newborns' livers take a while to kick in.
The autism-jaundice link was not seen in Danish children born prematurely. The authors said brain development near birth might be most vulnerable to high bilirubin levels, but that's only speculation.