HealthDay News — Maternal prenatal weight gain is associated with an increased risk for autism spectrum disorders, but pre-pregnancy BMI is not, researchers have found.

“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,” Deborah A. Bilder, MD, from the University of Utah in Salt Lake City, and colleagues reported in Pediatrics.

She and colleagues hypothesized that changes in the fetal steroid hormone environment may play a role in the etiology of autism. Because previous studies have shown pre-pregnancy BMI and pregnancy weight gain to be a marker for steroid hormone exposure in other disease states, Bilder and colleagues examined their role in ASD risk in two cohorts.

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These included 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.

There was a significant association between ASD risk and pregnancy weight gain in population and research-based cohorts (adjusted odds ratios, 1.10 and 1.17, respectively, for each five pounds of weight gained), the researchers found. Pre-pregnancy BMI was not associated with ASD risk. These associations remained significant when analyses were restricted to ASD cases with normal IQ.

“This justifies an investigation into phenomena that link pregnancy weight gain and ASD independent of pre-pregnancy BMI,” the researchers wrote. 


  1. Bilder DA et al. Pediatrics. 2013; doi: 10.1542/peds.2013-1188.