Infants born with jaundice are at much greater risk of developing autism, a study published Monday showed.
The study published in the US journal Pediatrics found full-term infants born in Denmark between 1994 and 2004 who had jaundice were 67 percent more likely to develop autism.
Neonatal jaundice is usually caused by elevated production of bilirubin, a substance found in bile that results from the normal breakdown of red blood cells.
Jaundice is seen in 60 percent of term infants and usually resolves within the first week of life, but prolonged exposure to high bilirubin levels is neurotoxic and can cause lifelong developmental problems, the study says.
In this study researchers found the risk of autism was higher if the mother had had previous children, or, somewhat oddly, if the child was born between October and March.
The risk for autism disappeared if the child was a firstborn child or was born between April and September. Authors suggest the seasonal difference may be due to different levels of exposure to daylight, which has an effect on jaundice, or due to infections.
The difference in risk in firstborn versus subsequent children could be due to different levels of antibodies in women who have had multiple pregnancies, or it could reflect different levels of access to health care in the first days after delivery.
In Denmark, women with healthy term newborns who have already had children are discharged soon after delivery. Women having their first child remain in the hospital for three to four days, and so jaundice may be diagnosed while the infant is still in the hospital.
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