TABLE 1 

Distribution of characteristics among study subjects

CharacteristicNo. (%) of subjects by groupP value
ASDControl
Total no. of mothers in the study442464
Maternal characteristics
    Age, yr0.13
        <2578 (17.6)59 (12.7)
        25–29138 (31.2)138 (29.7)
        30–34153 (34.6)184 (39.7)
        ≥3573 (16.5)83 (17.9)
    Education, yr0.15
        <1251 (11.5)44 (9.5)
        12136 (30.8)138 (29.7)
        13–16143 (32.4)156 (33.6)
        ≥1768 (15.4)100 (21.6)
        Missing data44 (10.0)26 (5.6)
    Occupation0.77
        Employed/student353 (79.9)394 (84.9)
        Unemployed/benefits44 (10.0)46 (9.9)
        Missing data45 (10.2)24 (5.2)
    Smoking during pregnancy0.21
        No352 (79.6)400 (86.2)
        Yes60 (13.6)53 (11.4)
        Missing data30 (6.8)11 (2.4)
    Parity0.01
        0236 (53.4)208 (44.8)
        ≥1206 (46.6)256 (55.2)
    Living status0.75
        Married/cohabiting384 (86.9)424 (91.4)
        Single/other22 (5.0)22 (4.7)
        Missing data36 (8.1)18 (3.9)
Paternal characteristics
    Age, yr0.43
        <2533 (7.5)29 (6.3)
        25–29110 (24.9)97 (20.9)
        30–34156 (35.3)177 (38.1)
        35–3986 (19.5)106 (22.8)
        ≥4054 (12.2)54 (11.6)
        Missing data3 (0.7)1 (0.2)
    Education, yr0.20
        <1263 (14.3)54 (11.6)
        12168 (38.0)170 (36.6)
        13–1677 (17.4)104 (22.4)
        ≥1767 (15.2)82 (17.7)
        Missing data67 (15.2)54 (11.6)
    Occupation0.06
        Employed/student369 (83.5)432 (93.1)
        Unemployed/benefits19 (4.3)11 (2.4)
        Missing data54 (12.2)21 (4.5)
Sex of child0.16
    Boy364 (82.4)365 (78.7)
    Girl78 (17.6)99 (21.3)