In Reply Our study focused on the narrow category of autistic disorder (infantile/childhood autism) and on mental retardation. We did not examine whether IVF was related to other diagnoses within the ASD category. The focus on autistic disorder was implemented to maximize diagnostic consistency across classification schemes and increase accuracy.1
Including ASDs in the outcome could potentially introduce residual confounding or confounding by calendar time because until 1999, only diagnoses obtained from hospitalized patients were reported to the Swedish registry. Information about diagnosis in outpatient clinics (where less severe cases of autism are most likely to be managed) was only introduced later.
Sandin S, Hultman C, Reichenberg A. Autism in Children Born After In Vitro Fertilization—Reply. JAMA. 2013;310(19):2101. doi:10.1001/jama.2013.278610