Feasibility and preliminary efficacy of an infant preemptive intervention for prodromes of autism spectrum disorder (ASD) delivered within an Italian tertiary hospital

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with early-emerging social-communication atypicalities, yet diagnosis and access to specialized intervention often occur years after prodromal signs first appear. Preemptive, parent-mediated Naturalistic Developmental Behavioral Interventions (NDBIs) delivered in the first year of life have shown promise, but evidence for their feasibility and clinical impact within routine public services remains limited. This pilot study examined the feasibility, acceptability, and preliminary efficacy of FIRRST (Fostering Infant Responsivity and Reciprocity-Support to Thrive), a telehealth NDBI program for infants under 15 months with early signs of ASD, implemented in an Italian tertiary child neuropsychiatric hospital. Methods: = 30) participated in weekly, 1-h, telehealth, parent-mediated FIRRST sessions for six months, delivered by trained clinicians and supporting social engagement, communication, play, motor development, and environmental enrichment within everyday routines. Feasibility and acceptability outcomes included recruitment, retention, and a parent satisfaction questionnaire, while caregiver implementation of NDBI strategies (MONSI-CC) was the primary clinical outcome; secondary outcomes were children's ASD symptoms (BOSCC), developmental level (Griffiths III), adaptive functioning (Vineland-II), and parental stress (PSI-4), assessed at baseline (T0), 3 months (T1), and post-intervention (T2) using repeated-measures ANOVA. Results: Of 44 screened families, 30 were enrolled and 28 completed the full program, yielding an attrition rate of 6.7%; dropouts were attributed to practical constraints rather than intervention-related factors. Parental satisfaction ratings were predominantly positive across domains of perceived usefulness, therapeutic alliance, and impact on the child's enjoyment and social engagement. Caregivers showed significant, progressive improvements from T0 to T2 across all MONSI-CC domains and total score, paralleled by significant reductions in BOSCC social-communication and restricted and repetitive behavior scores and gains in Griffiths III and Vineland-II domain and composite scores, whereas PSI-4 total and subscale scores did not show significant change over time. Among the 17 children eligible for the ADOS-2 Toddler Module at T2, mean total and domain scores were in the low range, consistent with relatively mild ASD symptom expression at post-intervention. Discussion: FIRRST was feasible and acceptable for families of infants with ASD prodromes within a public child neuropsychiatric hospital, with high retention and strong caregiver endorsement of the telehealth, parent-mediated format. The pattern of increased caregiver NDBI strategy fidelity alongside reductions in early ASD symptoms and improvements in developmental and adaptive functioning suggests that a very-early, family-centered, telehealth NDBI may positively support early trajectories for a subset of infants at elevated likelihood for ASD. These pilot findings support the implementation of a larger multicenter randomized controlled trial rigorously evaluating FIRRST and underscore the potential of first-year preemptive intervention embedded in public health systems.