Elevated pesticide levels in pregnant women are associated with an increased risk of autism among their children, says a study.

Autism is a complex neurodevelopmental disorder with largely unknown causes. It is characterised by problems with communication, difficulty relating to people and events, and repetitive body movements or behaviours.

"These findings provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism among offspring," the researchers said.

The study, published online in the American Journal of Psychiatry, examined whether elevated maternal levels of persistent organic pollutants are associated with autism among children.

Persistent organic pollutants are toxic chemicals that adversely affect human health and the environment around the world.

The researchers, including Professor Alan Brown from Columbia University Medical Centre in the US, analysed levels of DDE, a breakdown product of the pesticide DDT (dichlorodiphenyltrichloroethane).

Although DDT and other persistent organic pollutants were widely banned in many countries decades ago, they persist in the food chain, resulting in continuous exposure among populations.

These chemicals transfer across the placenta, resulting in potential prenatal exposure among nearly all children.

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The researchers evaluated levels of DDE in maternal serum samples drawn from more than 750 children with autism and matched control participants from a national birth cohort study, the Finnish Prenatal Study of Autism.

The odds of autism among children were significantly increased in mothers whose DDE levels were elevated (defined as the 75th percentile or greater).

In addition, the odds of children having autism with intellectual disability were increased more than twofold with maternal DDE levels above this threshold, the study said. (IANS)