A Comparison of Children Born Preterm and Full-Term on the Autism Spectrum in a Prospective Community Sample

Prematurity and Genetic Liability for Autism Spectrum Disorder

Background

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterized by diverse presentations and a strong genetic component. Environmental factors, such as prematurity, have also been linked to increased liability for ASD, though the interaction between genetic predisposition and prematurity remains unclear. This study aims to investigate the impact of genetic liability and preterm birth on ASD conditions.

Methods

We analyzed phenotype and genetic data from two large ASD cohorts, the Simons Foundation Powering Autism Research for Knowledge (SPARK) and Simons Simplex Collection (SSC), encompassing 78,559 individuals for phenotype analysis, 12,519 individuals with genome sequencing data, and 8,104 individuals with exome sequencing data. Statistical significance of differences in clinical measures were evaluated between individuals with different ASD and preterm status. We assessed the rare variants burden using generalized estimating equations (GEE) models and polygenic load using ASD-associated polygenic risk score (PRS). Furthermore, we developed a machine learning model to predict ASD in preterm children using phenotype and genetic features available at birth.

Results

Individuals with both preterm birth and ASD exhibit more severe phenotypic outcomes despite similar levels of genetic liability for ASD across the term and preterm groups. Notable, preterm ASD individuals showed an elevated rate of de novo variants identified in exome sequencing (GEE model with Poisson family, p-value = 0.005) in comparison to the non-ASD preterm group. Additionally, a GEE model showed that a higher ASD PRS, preterm birth, and male sex were positively associated with a higher predicted probability for ASD, reaching a probability close to 90%. Lastly, we developed a machine learning model using phenotype and genetic features available at birth with limited predictive power (AUROC = 0.65).

Conclusions

Preterm birth may exacerbate the multimorbidity present in ASD, which was not due to the ASD genetic factors. However, increased genetic factors may elevate the likelihood of a preterm child being diagnosed with ASD. Additionally, a polygenic load of ASD-associated variants had an additive role with preterm birth in the predicted probability for ASD, especially for boys. We propose that incorporating genetic assessment into neonatal care could benefit early ASD identification and intervention for preterm infants.

Comparing autism phenotypes in children born extremely preterm and born at term

Children born preterm are at increased risk for autism spectrum disorder (ASD). There is limited knowledge about whether ASD phenotypes in children born preterm differ from children born at term. The objective of this study was to compare ASD core symptoms and associated characteristics among extremely preterm (EP) and term-born children with ASD. EP participants (n = 59) from the Extremely Low Gestational Age Newborn Study who met diagnostic criteria for ASD at approximately 10 years of age were matched with term-born participants from the Simons Simplex Collection on age, sex, spoken language level, and nonverbal IQ. Core ASD symptomatology was evaluated with the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). Developmental milestones, anthropometrics, seizure disorder, and psychiatric symptoms were also investigated. The EP group had lower parent-reported symptom scores on ADI-R verbal communication, specifically stereotyped language, and restricted, repetitive behaviors. There were no between-group differences on ADI-R nonverbal communication and ADI-R reciprocal social interaction or with direct observation on the ADOS-2. The EP group was more likely to have delayed speech milestones and lower physical growth parameters. Results from female-only analyses were similar to those from whole-group analyses. In sum, behavioral presentation was similar between EP and IQ- and sex-matched term-born children assessed at age 10 years, with the exception of less severe retrospectively reported stereotyped behaviors, lower physical growth parameters, and increased delays in language milestones among EP-born children with ASD.

Autistic traits of children born very preterm assessed using Autism Diagnostic Observation Schedule, Second Edition

Preterm birth has been linked with increased incidence of autism spectrum disorder (ASD). Despite the remarkable difference in the clinical backgrounds between ASD children born preterm and term, cross-sectional studies have found no striking difference in their autistic traits. To highlight autistic traits related with preterm birth, children born very preterm (prospective birth cohort, n = 50) and term (case cohort, n = 16), who were diagnosed as "Autism" by the Autism Diagnostic Observation Schedule (ADOS), 2nd edition, were compared using the calibrated severity scores of ADOS-2 and T-scores of the Social Responsiveness Scale, 2nd edition. No significant difference was found in the calibrated severity scores between ASD children born preterm and term. There was a trend that T-scores were smaller for the preterm cohort, which did not reach a statistical significance. Even when detailed cross-sectional information was obtained using ADOS-2, no difference in autistic traits was observed between children born very preterm and term. Our findings were consistent with a previous study, which assessed the entire prospective cohort of children born very preterm and found no difference in original ADOS scores. Further studies are warranted to delineate how preterm birth affects the autistic traits and their parental perception in a large prospective cohort.

The critical importance of follow-up to school age: Contributions of the NICHD Neonatal Research Network

Follow-up studies are essential for understanding outcomes and informing the care of infants with high risk for medical and developmental consequences because of extreme prematurity or perinatal illness. Studies that extend to school age often identify sequelae that go unrecognized in neonatal or short-term follow-up studies. Many critical neurocognitive, behavioral, functional, and health outcomes are best assessed beginning at school age. The Eunice Kennedy Shriver National Institute of Child Health and Development Neonatal Research Network (NRN) has performed comprehensive school age evaluations of several key trial cohorts. This manuscript summarizes the important contributions of school age follow-up studies in the NRN, both historically and in ongoing research. We describe in detail the clinical questions that have been answered by the completed studies and new questions about the outcomes of high-risk infants that must be addressed by ongoing and future studies.