Characteristics of Study Participants

CharacteristicChildren With ASD (N = 256), %Controls (N = 752), %Pa
Child's year of birth
Child's age at time of interview/assessment, y
Birth weight, g
Biological mother's age at birth of child, y
Biological father's age at birth of child, y
Mother's education level
    No diploma33.75
    High school graduate1515
    Some college1922
    College graduate6360
Single parent
  • Percentages of cases and controls were not exactly identical on matching variables (birth year, gender, MCO) because we did not always get exactly 3 matched controls per case within each matching stratum.

  • a P for χ2 test of independence between row (characteristic of study participant) and column (ASD case versus control).

  • b Recruitment of controls lagged behind case-children so that controls could be recruited to match case-children who had agreed to participate within birth year, gender, and MCO matching strata. The lagged recruitment meant that controls were an average of 3 months older than case-children at the time of interview/assessment.