Risk factors for autism and Asperger syndrome. Perinatal factors and migration.

Using the Swedish Medical Birth Registry (MBR), obstetrical and demographic information was retrieved for 250 children with autism or Asperger syndrome who were born in Malmoe, Sweden, and enrolled at the local Child and Youth Habilitation Center. The reference group consisted of all children born in Malmoe during 1980-2005. Obstetric sub-optimality (prematurity, low Apgar scores, growth restriction, or macrosomia) was positively associated with autism but not with Asperger syndrome. Maternal birth outside the Nordic countries was positively associated with autism (adjusted OR: 2.2; 95%CI: 1.6-3.1) and negatively associated with Asperger syndrome (OR: 0.6; 95%CI: 0.3-0.97). The highest risk estimate for autism was found among children to women who were born in sub-Saharan Africa (OR: 7.3), or in East Asia (OR: 3.4).