Preterm Birth Linked to Increased Risk of Autism

Preterm and early birth is associated with an increased risk of autism spectrum disorder (ASD), independent of genetic or environmental factors, according to a new study.

Researchers at Lund University (LU; Malmö, Sweden) and the Icahn School of Medicine at Mount Sinai (MSSM; New York, NY, USA) conducted a national cohort study that included all 4,061,795 singleton infants born in Sweden during 1973–2013 who survived to age one year, and who were followed-up for ASD, as identified from nationwide outpatient and inpatient diagnoses through 2015. The study wished to examine whether gestational age at birth was associated with ASD. Co-sibling analyses were used to assess the influence of unmeasured shared familial (genetic and/or environmental) factors.


The results showed that ASD prevalence, as reflected by gestational age at birth, were 6.1% for extremely preterm (22–27 weeks), 2.6% for very to moderate preterm (28–33 weeks), 1.9% for late preterm (34–36 weeks), 2.1% for all preterm (lower than 37 weeks), 1.6% for early term (37–38 weeks), and 1.4% for term (39–41 weeks) births. Adjusted prevalence ratios comparing extremely preterm, all preterm, or early term (versus term) were 3.72, 1.35, and 1.11 in boys, and 4.19, 1.53, and 1.16, among girls, respectively. These associations were only slightly offset after controlling for shared familial factors. The study was published in the August 2021 issue of Pediatrics.

“Children born prematurely need early evaluation and long-term follow-up to facilitate timely detection and treatment of autism, especially those born at the earliest gestational ages,” said lead author Casey Crump, MD, PhD, of MSSM. “More research is needed to understand the biologic mechanisms linking preterm birth with higher risks of autism. In patients of all ages, gestational age at birth should be routinely included in history-taking and medical records to help identify in clinical practice those born preterm or early term.”

ASD affects six per 1,000 children, and occurs more often among boys than girls. ASD affect three different areas of a child's life - social interaction, communication (both verbal and non-verbal), and behaviors and interests. The three main types are Asperger's syndrome, pervasive developmental disorder, not otherwise specified (PDD-NOS), and autistic disorder. The DSM -5 also included two rare but severe autistic-like conditions, called Rett syndrome and childhood disintegrative disorder.

Related Links:
Lund University
Icahn School of Medicine at Mount Sinai