Researchers have been documenting the many factors associated with the development of autism spectrum disorders (ASD) in pregnant women. A study from the University of Utah has found another piece of the puzzle by linking a “modest yet consistent increase in pregnancy weight gain” with later diagnosis of an ASD in the child. While several studies have worked with pregnancy weight gain and the mother’s body mass index (BMI) as a factor in ASD risk, this is the first study to control for BMI and the weight of the mother at the start of pregnancy. The researchers ultimately connected a particular pattern of weight gain with ASD risk, but they emphasize that pregnant women should not limit their food intake to mitigate the risk. The weight gain pattern is likely a product of some other process like hormonal imbalance or immune system problems, which are also linked to the development of ASD.

The researchers examined two sets of data, both culled from the Utah Registry of Autism and Developmental Disabilities, a database maintained by the Utah Department of Health. The first group involved a comparison of eight-year-olds in several Utah counties. It was comprised of 128 children diagnosed with ASD and an age- and gender-matched control group of 10,920 children. The second study group focused on 288 Utah children who were diagnosed with ASD, but whose siblings did not have an autism spectrum disorder.

In both groups, the researchers observed the same pattern of pregnancy weight gain during the gestation of the child who was later diagnosed with ASD. They found that the woman’s BMI at the start of the pregnancy was not associated with autism in the child, but a particular type of incremental weight gain was. These findings may help direct further research as scientists attempt to pin down the exact causes of ASD.

According to lead study author Deborah Bilder, M.D., assistant professor of psychiatry at the University of Utah, “These findings suggest that weight gain during pregnancy is not the cause of ASD but rather may reflect an underlying process that it shares with autism spectrum disorders, such as abnormal hormone levels or inflammation.”

This research is published in the journal Pediatrics.

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