Moderate to Late Preterm Birth Has a Negative Impact on Cognitive Profile in Autism

Background: Despite the growing number of cohort studies examining the risk of autism based on prematurity, few studies have looked at neurodevelopmental profiles of children with autism born prematurely. Moreover, although data on the outcome of children born very preterm before 32 Weeks of Amenorrhea (WA) is now abundant, the later outcome of children born moderately to late preterm (MLPT, 32⁺⁰ and 36⁺⁶ WA) and those born early term (ET, 37⁺⁰ and 38⁺⁶ WA) remains uncertain - this population being less systematically followed.

Objectives: to characterize the neurodevelopmental profiles of children with autism born MLPT, ET and full term FT (over 39⁺⁰ WA), using validated tools which assess autistic behaviors and cognitive level.

Methods: 415 children with Autism Spectrum Disorder (ASD) were followed up in the University Child Psychiatry Center of Tours (France) in 2010-2016. 28 (6.8%) were MLPT, 104 (25%) ET and 283 FT (68.2%). They were diagnosed by a multidisciplinary team according to DSM-4-TR criteria; ADI-R and ADOS complemented the diagnosis of ASD.

Neurodevelopmental profiles including cognitive level and autistic behaviors were determined, at median age of 6 years 9 months using validated tools. Cognitive assessment (verbal and nonverbal developmental quotients) was carried out with age adapted neuropsychological tests. Behavioral assessment was carried out using the Childhood Autism Rating Scale (CARS, Schopler et al, 1980), the Revised Behavior Summarized Evaluation scale (BSE-R, Barthélémy et al, 1997) and the Repetitive and Restricted Behavior scale (RRB, Bourreau et al, 2009).

Results: Within the total sample, 209 patients (50.4%) had an Autistic Disorder, 21 (5%) an Asperger Syndrome and 185 (44.6%) a pervasive developmental disorder not otherwise specified (PDD-NOS). No significant difference was observed between the three groups MLPT, ET and FT (χ²=4.42; df 4; p=0.35). The autistic profiles assessed by the CARS, BSE-R and RRB scales, did not differ between these three groups of patients. No significant difference was also found for the presence or absence of an intellectual disability ID (χ²=3.91; df 2; p=0.14). However, ID was significantly deeper to severe in premature patients compared to those born ET and FT (χ²=12.1; df 4; p=0.017). This cognitive effect was related to a significant lower nonverbal developmental quotient in the MLPT patients compared to those born FT (p=0.006 at post-hoc tests).

Conclusions: Moderately to late preterm birth does not modify autistic severity but exacerbates developmental deficiency and increases nonverbal difficulties in autism. These results highlight that, even moderate to late, preterm birth has a negative impact on cognitive profile in patients with neurodevelopmental vulnerability.