Gestational age and the risk of autism spectrum disorder in Sweden, Finland, and Norway: A cohort study

Introduction The complex etiology of autism spectrum disorder (ASD) is still unresolved. Preterm birth (
Martina Persson and co-workers study autism spectrum disorder and gestational age in three Nordic countries.
Author summary Why was this study done? Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent impairments in social communication and restricted and repetitive behaviors. The etiology remains unresolved. Length of gestation, including preterm birth, has been linked to risk of ASD, but reliable estimates of risks for the whole range of gestational ages (GAs) are lacking. The primary objective of this study was to provide a detailed and robust description of ASD risk across the entire range of GA while taking fetal sex and size at birth into account. What did the researchers do and find? This study was based on population-based data from national medical registries in three Nordic countries—Sweden, Finland, and Norway—and included 3,526,174 singletons born 1995 to 2015. Relative risks (RRs) of ASD by GA at birth were estimated with log binominal regression. The RR of ASD increased by each week of GA, pre- as well as postterm, from 40 to 24 weeks of gestation and from 40 to 44 weeks of gestation, independently of sex and birth weight for GA. What do these findings mean? On a population level, the risks of ASD were increased in children born either pre- or postterm, including children born close to week 40. We found that the risk of ASD increased weekly, with each week further away from 40 weeks of gestation.