(HealthDay News) – The risk of autism spectrum disorders (ASD) is increased with maternal prenatal weight gain, but is not associated with pre-pregnancy body mass index (BMI), according to a study published online Oct. 28 in Pediatrics.

Deborah A. Bilder, MD, from the University of Utah in Salt Lake City, and colleagues examined the correlation between pre-pregnancy BMI and pregnancy weight gain and ASD risk. Data were obtained from two cohorts: a population-based ASD cohort (128 cases) from a three-county surveillance area, gender- and age-matched with 10,920 controls; and a research-based ASD cohort, including 288 cases and their 493 unaffected siblings. Birth certificate records were used to ascertain prenatal variables.

The researchers observed a significant association between ASD risk and pregnancy weight gain in population and research-based cohorts (adjusted odds ratios, 1.1 and 1.17, respectively, for each five pounds of weight gained). Pre-pregnancy BMI was not associated with ASD risk. These associations remained significant when analyses were restricted to ASD cases with normal IQ.

“ASD risk associated with a modest yet consistent increase in pregnancy weight gain suggests that pregnancy weight gain may serve as an important marker for autism’s underlying gestational etiology,” the authors conclude. “This justifies an investigation into phenomena that link pregnancy weight gain and ASD independent of pre-pregnancy BMI.”

Two authors disclosed financial ties to the pharmaceutical industry; one author holds a patent with Lineagen.

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