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Table 1 Maternal and child characteristics

From: Air pollution, fetal and infant tobacco smoke exposure, and wheezing in preschool children: a population-based prospective birth cohort

  n = 4,634
  Observed After multiple imputations
Maternal characteristics   
Age (years)* 31.1 (4.9) 31.1 (4.9)
Highest completed education (%)   
 Non-completed, primary or secondary 47.1 (2,050) 48.2 (2,234)
 Higher 52.9 (2,299) 51.8 (2,400)
Missing 6.2 (285) -
Parity (%)   
 Nulliparity 61.6 (2,762) 61.4 (2,844)
 Multiparity 38.4 (1,722) 38.6 (1,790)
Missing 3.2 (150) -
History of asthma or atopy (%)   
 No 61.9 (2,369) 59.0 (3,734)
 Yes 38.1 (1,460) 41.0 (1,900)
Missing 17.4 (805) -
Fetal and Child characteristics   
Male sex (%) 49.9 (2,313) 49.9 (2,313)
Gestational age at birth (weeks)$ 39.9 (37.0-42.1) 39.9 (37.0-42.1)
Birth weight (grams)* 3,439 (556) 3,439 (556)
Ethnicity (%)   
 European 70.4 (3,144) 69.9 (3,240)
 Non-European 29.6 (1,320) 30.1 (1,394)
Missing 3.7 (170) -
Breastfed (%)   
 No 7.7 (339) 8.0 (371)
 Yes 92.3 (4,089) 92.0 (4,263)
Missing 4.4 (206) -
Day care attendance (%)   
 No 48.0 (1,894) 50.0 (2,316)
 Yes 52.0 (2,050) 50.0 (2,318)
Missing 14.9 (690) -
Pet keeping (%)   
 No 65.5 (2,399) 64.6 (2,993)
 Yes 34.5 (1,263) 35.4 (1,641)
Missing 21.0 (972) -
Lower respiratory tract infections age 1 year (%)   
 No 86.4 (3,165) 85.4 (3,957)
 Yes 13.6 (498) 14.6 (677)
Missing 21.0 (971) -
Lower respiratory tract infections age 2 years (%)   
 No 87.9 (3,494) 87.4 (4,052)
 Yes 12.1 (484) 12.6 (582)
Missing 14.2 (659) -
Lower respiratory tract infections age 3 years (%)   
 No 93.3 (3,453) 92.7 (4,294)
 Yes 6.7 (247) 7.3 (340)
Missing 20.2 (934) -
Smoking of father (%)   
 No 57.4 (2,153) 57.4 (2,658)
 Yes 42.6 (1,599) 42.6 (1,976)
Missing 19.0 (882) -
Fetal smoke exposure (%)   
 No 86.9 (3,246) 86.4 (4003)
 Yes 13.1 (489) 13.6 (631)
Missing 19.4 (899) -
Infant smoke exposure (%)   
 No 82.3 (3,391) 81.4 (3,770)
 Yes 17.7 (728) 18.6 (864)
Missing 11.1 (515) -
Wheezing age 1 year (%)   
 No 74.0 (2,922) 74.1 (3,433)
 Yes 26.0 (1,028) 25.9 (1,201)
Missing 14.8 (684) -
Wheezing age 2 years (%)   
 No 82.1 (3,358) 82.6 (3,827)
 Yes 17.9 (731) 17.4 (807)
Missing 11.8 (545) -
Wheezing age 3 years (%)   
 No 89.0 (3,417) 89.4 (4,143)
 Yes 11.0 (421) 10.6 (491)
Missing 17.2 (796) -
  1. Values are percentages (absolute values), means (SD)* or medians (5-95th percentile)$.
  2. Missing percentages are given for the total population of analysis n = 4634. Other percentages are valid percentages.