Purpose: To determine whether prepregnancy weight was associated with children's birth weight, early physical growth, and autism diagnosis.
Design: Early Childhood Longitudinal Study-Birth Cohort data.
Setting: United States.
Subjects: Representative sample of U.S. children followed from birth through kindergarten (n = 4800). Also, a subpopulation of the very low birth weight children was examined (n = 500).
Measures: Maternal variables included age and prepregnancy body mass index. Changes in children's height, weight, and head circumference between 9 months and 2 years were used as growth metrics. Children's sex, age, birth weight, and reported autism were also considered.
Analysis: Logistic and multinomial logistic models assessed the impact of prepregnancy weight on birth weight and children's subsequent rate of physical growth and autism.
Results: Children born to underweight or obese mothers had increased odds of very low birth weight. Very low birth weight was related to rapid height and weight growth and more than twice the likelihood to subsequently be diagnosed with autism. For the subgroup of very low birth weight children, rapid head growth was related to a fivefold increase in the odds of autism. After accounting for the impact birth weight and growth rates, we found prepregnancy weight indirectly impacted autism risk.
Conclusion: Being underweight or obese during prepregnancy indirectly increased risk for autism from increased odds of low birth weight and accelerated postnatal growth.