Gestational age impacts prevalence of psychiatric disorders, intellectual disability

Groups with shorter fetal maturity at birth had slightly higher rates of multiple neuropsychiatric disorders while groups with the longest fetal maturity exhibited the lowest rates for most disorders.

“We found that diagnosis of both child-onset and adult-onset neuropsychiatric diseases was associated with preterm birth, with a gradient of risk observed from very preterm (20-31 weeks) to late preterm (34-36 weeks) birth,” Yuntian Xia, MPH, of the Yale Center for Perinatal, Pediatric and Environmental Epidemiology, and colleagues wrote. “Our study also provides evidence of heterogeneity in long-term neuropsychiatric risk by gestational age within the term spectrum.”

Xia and colleagues evaluated the associations between gestational age groups and several major types and subtypes of childhood and adult-onset neuropsychiatric disorders. In this nationwide, registry-based cohort study, the researchers evaluated data from a national register of 2,327,639 births in Denmark from Jan. 1, 1978, to Dec. 31, 2016. Gestational age groups were classified as very preterm (20 to 31 completed weeks), moderately preterm (32 to 33 weeks), late preterm (43 to 36 weeks), early term (37 to 38 weeks), term (39 to 40 weeks) and late or postterm (41 to 45 weeks). The researchers compared gestational age with neuropsychiatric disorders using records from the Danish Psychiatric Central Register, applying Poisson regression to determine the rate ratio.

The major neuropsychiatric disorders included were mental and behavioral disorders due to psychoactive substance abuse, schizophrenia and related disorders, mood disorders, neurotic, stress-related and somatoform disorders, eating disorders, specific personality disorders, intellectual disability, pervasive developmental disorders and behavioral and emotional disorders with onset usually occurring in childhood and adolescence. The subtypes of common neuropsychiatric diseases included were mental and behavioral disorders due to alcohol use, mental and behavioral disorders due to cannabis use, schizophrenia, schizoaffective disorders, bipolar disorder, anorexia, childhood autism and hyperkinetic disorder.

Among the births evaluated, a majority of which were male, 1% were born very preterm, 0.9% moderately preterm, 4.3% late preterm, 16.7% early term, 51.5% at term and 25.7% late or postterm. The rate ratio of neuropsychiatric diagnoses decreased as gestational age increased. Individuals born at early term exhibited 7% higher rates of neuropsychiatric disorder diagnoses and a 31% higher rate of an intellectual disability compared with those born at term. The late or postterm group had lower rates for most disorders, except pervasive developmental disorders, which was higher for postterm births compared with at-term births.

Some misclassification of gestational age occurred, and other subtypes of neuropsychiatric disorders were not included, which affected the results.

“Our findings suggest that childhood and adult neuropsychiatric disorders might stem from factors related to early development,” Xia and colleagues wrote. “Intervention strategies targeted at perinatal risk factors and obstetric practices preventing nonoptimal delivery timing and improving postnatal care for those born with nonoptimal gestational duration might reduce long-term neuropsychiatric risk in the population.”