Profiles of Developmental Level, Adaptive Skills, and Diagnostic Symptoms in Late Preterm, Early Term, and Full Term Toddlers with Autism

Background: Limited research has examined risk for developmental difficulties, including autism, in infants considered late preterm (34-36 weeks gestation) or early term (37-38 weeks gestation), despite reports of increased morbidity in these groups compared with full term infants (39-40 weeks gestation). A study presented at IMFAR 2013 found that among toddlers with autism, those born during the late preterm period showed reduced symptoms of social affect dysfunction compared with those born after 38 weeks (Caravella et al., 2013). However, it is unknown how autism symptoms compare in individuals born in the early term versus full term or late preterm periods.

Objectives: Characterize developmental profiles and autism symptomatology in toddlers with autism who were born across late preterm, early term, and full term gestational periods.

Methods: Participants included 53 male toddlers with autism (M = 24.46 months, SD = 4.05 months) born during late preterm (n=11), early term (n=12), or full term (n=30) gestational periods. Participants were administered the Autism Diagnostic Observation Schedule (ADOS) and Mullen Scales of Early Learning to assess autism symptomatology and developmental level, respectively, while adaptive functioning was assessed with the Vineland Adaptive Behavior Scales, 2nd Edition, Survey Form.

Results: Greater gestational age was associated with higher overall autism symptomatology on the ADOS (r=0.282, p=0.041). Specifically, greater gestational age was associated with increased Social Affect symptoms (r=0.314, p=0.022) but not Restricted and Repetitive Behavior symptoms (r=0.023, p = NS). Greater gestational age was associated with reduced Receptive Language abilities (r=-0.320, p=0.019) as assessed with the Mullen. Greater gestational age was associated with lower adaptive skills in the domains of Communication (r=-0.340, p=0.013) and Daily Living Skills (r=-0.383, p=0.005), as well as a marginal association with Socialization abilities (r=-0.237, p=0.088).

Analyses based on group classifications found that toddlers with autism born at early term or full term did not differ in regards to their level of autism symptoms, developmental or adaptive functioning. Toddlers born at late preterm had reduced Social Affect symptoms of autism, greater receptive language abilities, and greater adaptive functioning in the domains of Communication, Daily Living Skills, and Socialization than infants born at full term (Cohen's d=0.66-1.18). Toddlers born at late preterm versus early term did not differ in regards to level of autism symptoms or developmental functioning but those born at late preterm demonstrated greater adaptive Communication and Daily Living skills (Cohen's d=0.84-1.47).

Conclusions: When examining profiles of toddlers with autism who were born during the late preterm, early term, and full term gestational periods, full term infants showed the greatest degree of autism symptomatology, particularly in regards to Social Affect impairments. A new classification system has been proposed to better capture the morbidity associated with early term births compared to full term births (Sengupta et al., 2013). This initial study suggests that with regards to autism symptomatology and developmental functioning, toddlers with autism who are born at early term do not present differently from those born at full term. Implications for factors affecting autism symptom presentation will be discussed.