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Table 1 Sample size (N), characteristics of participants and follow-up rate

From: Effect of tobacco smoke exposure during pregnancy and preschool age on growth from birth to adolescence: a cohort study

  1999-2000 2009-2011 Follow-up rate
Age in years - mean and (SD) 1.5 (1.4) 12.2 (1.5) -
  N (%) N (%) %
Age (in years)    
  <1 1186 (49.3) 842 (49.1) 71.0
  1-2 512 (21.3) 370 (21.5) 72.3
  >2 707 (29.4) 504 (29.4) 71.3
    p = 0.86
Gender    
  Male 1224 (50.9) 870 (50.7) 71.1
  Female 1181 (49.1) 846 (49.3) 71,6
    p = 0.76
Birth weight (g)    
  ≥ 4000 143 (6.9) 102 (5.9) 71.3
  3000-3999 1619 (67.6) 1160 (67.6) 71.7
  2500-2999 483 (20.1) 344 (20.1) 71.2
  < 2500 160 (6.4) 110 (6.4) 68.7
    p = 0.89
Height-for-age at birth (z-score) *    
  ≥ −2 z-score 270 (11.1) 195 (11.3) 72.2
  < −2 z-score 2123 (88.7) 1512 (62.9) 71.2
    p = 0.73
BMI-for-age (z-score)    
  Thinness (< −2 z-score) 68 (2.8) 41 (2.4) 60.3
  Adequate (≥ −2 to ≤ 1 z-score) 1857 (77.2) 1325 (77.2) 71.3
  Overweight (>1 to ≤ 2 z-score) 371 (15.4) 270 (15.7) 72.8
  Obesity (>2 z-score) 108 (4.5) 80 (4.7) 74.1
    p = 0.18
Height-for-age (z-score)    
  ≥ −2 z-score 146 (8.0) 90 (5.3) 61.6
  < −2 z-score 2258 (93.9) 1626 (94.8) 72.0
    p= 0.01
Socioeconomic position    
  A (high-income) 86 (3.6) 57 (3.3) 66.3
  B 289 (12.0) 206 (12.0) 71.3
  C 1019 (42.4) 743 (43.3) 72.9
  D 807 (33.5) 577 (33.6) 71.5
  E (low-income) 204 (8.5) 133 (7.7) 65.2
    p = 0.19
Maternal schooling (years)    
  ≥ 12 206 (8.6) 153 (8.9) 74.3
  9 – 11 638 (26.5) 480 (28.0) 75.2
  5 – 8 1363 (56.7) 956 (55.7) 70.1
  0 – 4 177 (7.4) 113 (6.6) 63.8
    p= 0.02
Maternal smoking during pregnancy    
  Yes 271 (11.3) 167 (9.7) 61.6
  No 2133 (88.7) 1549 (90.3) 72.6
    p< 0.01
  1. p value from Chi-square test; *No information for 12 children.
  2. According to the criteria of the Brazilian Marketing Research Association (2003): based on the number of home appliances, cars and paid maids, and education level of the head of household.
  3. In 1999, 21 mothers and 449 fathers didn’t live with their children.