In this latest study, the authors found that a much higher percentage of newborns between 1994 and 2004 who had developed jaundice had a risk of developing autism. None of them had been born prematurely.
The researchers gathered data on 35,000 newborns who had jaundice. Autism was eventually diagnosed in 577 of them. 9% of the children eventually diagnosed with autism had jaundice during their first days of life, compared to 3% of children without autism.
The authors explain that prolonged exposure to elevated bilirubin levels can cause developmental problems which can persist for the rest of the child's life. Many infants have some degree of jaundice, which usually clears up within a week of being born.
Higher autism risk among newborns with jaundice was more markedly noticed among babies in Denmark born between October and March (from late Autumn until late winter/early spring). They also reveal that the risk was also higher if the mother had already had children.
The risk of autism among newborns with jaundice was no higher if the baby was born during late Spring to early Autumn (April-September), compared to babies who did not have jaundice.
The two factors that suggest possible links during the Danish winter months are less exposure to sunlight and a higher risk of infections.
A mother carrying a first child has different levels of antibodies compared to a mother who has already had children and is pregnant, the authors write. There may also be a difference in access two health care immediately after giving birth (between first time mothers and mothers who have already had children). The researchers write that these two factors require further investigation.
A Danish woman who has already had children is discharged from hospital much earlier than a first-time mother, who stays in hospital for three or four days. Perhaps a higher number of babies with jaundice from first-time mothers are diagnosed.
The researchers concluded:
Gestational age, parity, and season of birth play important roles in this association.
The authors stress that their study did not look into the severity of jaundice.
"Neonatal Jaundice, Autism, and Other Disorders of Psychological Development"
Rikke Damkjaer Maimburget al
Published online October 11, 2010
Written by Christian Nordqvist