Autism spectrum disorder (ASD) is characterized by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviours. ASD is caused by a combination of genetic and environmental factors. Objective: to identify possible risk factors of ASD. Methods: The current study is a case-control study. We recruited 142 caregivers of the children to complete an interview questionnaire about risk factors for ASD. Seventy one (71) cases of autistic children were recruited from Postgraduate Childhood Studies Institute affiliated to Ain Shams University, and 71 normal children from outpatient pediatric clinics of the Ain Shams University hospital. Cases and controls were matched regarding age and sex. Results: Advanced paternal age at the time of conception, hypertension during pregnancy, postnatal hypoxia, positive family history of psychiatric diseases, and artificial feeding are risk factors for ASD. Also, folic acid supplementation during 1st trimester is found to be protective from autism. Recommendations: Folic acid supplementation to the mother before pregnancy and at the first trimester of pregnancy (at least 600 mcg per day) is mandatory.