Birth Weight & Gestation Age Associated with Autism

New research published in The American Journal of Psychiatry reveals a significant association between fetal growth and autism. The study, conducted by researchers at the University of Manchester in the U.K., utilized early ultrasound data from Sweden’s Stockholm Youth Cohort, which yielded a population of 589,114 children under the age of 17. The population included 4,283 children ultimately diagnosed with ASD, 1,755 with intellectual disability, and 2,528 without. Utilizing the Swedish Medical Birth Registry, study authors charted the populations’ deviance from normal fetal growth, finding that significant deviance from mean birth weight in either direction is associated with risk of ASD. Findings showed that risk increased with fetal growth 1.50 standard deviations below and 2.00 standard deviations above the mean for gestational age, which supports earlier research regarding the association between premature birth and risk for autism. Babies born weighing over 9 pounds 14 ounces had 60% higher risk for developing autism, while those born weighing 5.5 pounds or less had 63% higher risk. These associations are strong, leaving ample space for inference and a great foundation for future research. Study author Professor Kathryn Abel elaborated on findings saying, “Risk appeared particularly high in those babies where they were growing poorly and continued in utero until after 40 weeks. This may be because these infants were exposed the longest to unhealthy conditions within the mother’s womb.” Abel asserts that, because “fetal growth is influenced by genetic and non-genetic factors,” we can infer that “the processes that leads to ASD probably begin during fetal life.” In addition to the evidence of the relationship between fetal growth, or birth weight, and risk of ASD, the study found specific significance in the association between below average fetal growth and ASD with intellectual disabilities.


Wood, Janice. “Extremes in Birth Weight Tied to Greater Risk of Autism | Psych Central News.” Psych N.p., 4 May 2013. Web. 07 May 2013. <>.

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