TABLE 1

Characteristics of Study Participants

CharacteristicChildren With ASD (N = 256), %Controls (N = 752), %Pa
MCO
    MCO-A44.49
    MCO-B4346
    MCO-C5449
Child's year of birth
    19941416.90
    19951515
    19961618
    19972119
    19981917
    19991414
Child's age at time of interview/assessment, y
    6105.04b
    72118
    81718
    92119
    101417
    111417
    1225
    130.40.3
Gender
    Female1315.37
    Male8785
Birth weight, g
    <100020.3.16
    1000–14990.41
    1500–249975
    2500–39997679
    >40001615
Biological mother's age at birth of child, y
    <2021.27
    20–2459
    25–292323
    30–343636
    ≥353530
Biological father's age at birth of child, y
    <2011.65
    20–292024
    30–396056
    40–491717
    ≥4922
Mother's education level
    No diploma33.75
    High school graduate1515
    Some college1922
    College graduate6360
Single parent
    No8285.29
    Yes1815
  • 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.