Oct. 11, 2010 -- As many as 60% of full-term newborns and 80% of babies born prematurely develop jaundice in their first few days of life. Now new research suggests the condition may be linked to a higher risk for autism.

Babies with jaundice develop yellowish skin due to excess of the chemical bilirubin, which is a byproduct of the breakdown of red blood cells. Most cases resolve within a week or two of birth. But in very rare cases, jaundice can result in brain damage, cerebral palsy, and even death.

The newly reported study included more than 700,000 children in Denmark. About 35,000 were diagnosed with jaundice as newborns.
More Babies With Jaundice Diagnosed With Autism

Babies who developed jaundice were 67% more likely to be diagnosed with autism during early childhood.

The risk was even higher for babies born in the fall and winter. The risk disappeared in babies whose mothers had not given birth before and in babies born in the spring and summer.

The study suggests a link between jaundice and autism, but it is not clear what that link is, study researcher Rikke Damkjaer Maimburg, PhD, of Denmark’s Aarhus University School of Public Health, tells WebMD.

“We can’t say from a study like this one that the association is causal, so parents shouldn’t worry that a child who has jaundice will develop autism,” she says. “It may be some genetic predisposition is associated with the development of jaundice and autism.”

Published today in the online issue of the journal Pediatrics, the study included all children born in Denmark between 1994 and 2004. Almost 36,000 developed jaundice and 532 were later diagnosed with autism spectrum disorder.
Winter Babies Most at Risk

Among children who developed autism, those born in the fall and winter were almost twice as likely to have had jaundice following birth as those born in the spring and summer.

Exposure to sunlight breaks down bilirubin and is considered protective against jaundice. Several studies have also suggested a link between autism and lack of vitamin D, which is known as the sunshine vitamin because the body produces it in response to sun exposure.

“Children born in the winter are also kept indoors more, exposing them to more infections,” Maimburg says. “This might also have an impact on autism risk, although this is just speculation.”

While there is widespread agreement that both genetic and environmental factors influence autism risk, researchers have yet to identify specific environmental risk factors for the disorder.

Earlier research by the Danish researchers also showed the jaundice-autism link, but findings from a California study published in 2005 showed no association.

Alycia Halladay, PhD, who is director of research for the advocacy group Autism Speaks, says parents should not be concerned that their children will develop autism if they had jaundice as newborns.

“This study does not address whether jaundice or elevated bilirubin plays a causal role in autism,” she says.

Autism Speaks is funding a study designed to determine if vitamin D deficiency in newborns is linked to autism.