This study compared clinical features, symptom severity, and prenatal/perinatal risk factors in children with regressive (ASD-R) and non-regressive autism spectrum disorder (ASD-NR) in a Turkish paediatric sample. A retrospective cross-sectional study was conducted with 143 children aged 2-6 years diagnosed with ASD, grouped as ASD-R (n = 29) or ASD-NR (n = 114). Symptom severity was assessed using the CARS, AuBC, and ABC. Data on prenatal and perinatal factors, epilepsy, and parental age were collected. No significant differences were found in CARS, AuBC, or total ABC scores, except for higher lethargy/social withdrawal scores in the ASD-NR group. Prenatal and perinatal risk factors and epilepsy prevalence were similar. However, parental ages at birth were significantly higher in the ASD-R group. Logistic regression did not yield significant predictors of regression. The findings suggest that prenatal and perinatal factors may influence developmental regression in ASD when interacting with genetic vulnerability. Longitudinal studies are needed to clarify the role of early environmental exposures and epigenetic mechanisms in regression patterns.