TABLE 1

Maternal and Infant Characteristics of the Study Population

Infants (N = 4164)
Mother
    Maternal age, mean (SD), y31.1 (4.8)
    Education, % (n)
        Low6.2 (246)
        Intermediate38.7 (1538)
        High55.2 (2195)
    Non-Dutch ethnicity, % (n)38.9 (1574)
    Smoking, % (n)16.2 (647)
Infant
    Girl50.6 (2107)
    Gestational age, median (95% range), wk40.1 (37.1–42.1)
    Birth weight, mean (SD), g3456 (547)
    Siblings, ≥1, % (n)40.2 (1604)
    Day care attendance, % (n)49.7 (1949)
Family history of asthma, house dust mite allergy, and hay fever, % (n)59.0 (1839)
Duration of breastfeeding, % (n)
    Never12.5 (519)
    <4 mo29.1 (1203)
    4–6 mo24.5 (1012)
    ≥6 mo33.9 (1404)
Duration of exclusive breastfeeding, % (n)
    Never12.8 (519)
    Partial for <4 mo, not breastfed thereafter29.2 (1182)
    Partial for 4–6 mo28.8 (1166)
    Exclusive for 4 mo, not breastfed thereafter2.0 (80)
    Exclusive for 4 mo, partially breastfed thereafter25.7 (1037)
    Exclusive for 6 mo1.4 (58)
Doctor-attended infectious diseases at ≤6 mo, % (n)
    URTI39.5 (1644)
    LRTI7.8 (323)
    GI7.6 (309)
Doctor-attended infectious diseases at 7–12 mo, % (n)
    URTI26.6 (912)
    LRTI10.2 (360)
    GI8.7 (295)
  • Data were missing on education (n = 185), ethnicity (n = 121), smoking (n = 170), birth weight (n = 3), siblings (n = 171), day care attendance (n = 240), family history of asthma, house dust mite allergy, and hay fever (n = 1046), duration of breastfeeding (n = 26), and duration of exclusive breastfeeding (n = 122). Data were missing for questionnaires at age 6 months for upper respiratory tract infections (n = 2), lower respiratory tract infections (n = 36), and gastrointestinal infections (n = 92) and at age 12 months for upper respiratory tract infections (n = 737), lower respiratory tract infections (n = 644), and gastrointestinal infections (n = 772). URTI indicates upper respiratory tract infection; LRTI, lower respiratory tract infection; GI, gastrointestinal infection.