Low but increasing prevalence of autism spectrum disorders in a French area from register-based data.

Register-based prevalence rates of childhood autism (CA), Asperger's syndrome (AS) and other autism spectrum disorders (ASD) were calculated among children aged 7 years old of the 1997-2003 birth cohorts, living in four counties in France. The proportion of children presenting comorbidities was reported. 1123 children with ASD were recorded (M/F ratio: 4.1), representing an overall prevalence rate of 36.5/10,000 children (95 % CI 34.4-38.7): 8.8/10,000 for CA (95 % CI 7.8-9.9), 1.7/10,000 for AS (95 % CI 1.3-2.3) and 25.9/10,000 for other ASD (95 % CI 24.2-27.8). ASD prevalence significantly increased (p < 0.0001) during the period under study. The proportion of children with an intellectual disability was 47.3 %, all other comorbidities were present in less than 5 % of the cases.