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Table 2 Percentage distribution of values of each factor in each group of children, with chi-square tests of association

From: Influence of maternal and perinatal factors on subsequent hospitalisation for asthma in children: evidence from the Oxford record linkage study

  % of each group of children Chi2 (df), with p value below
  All asthma
(N = 4017)
Asthma, aged 0-1
(N = 535)
Asthma, aged 2+
(N = 3482)
No asthma
(N = 244595)
All asthma Asthma aged 0-1 Asthma aged 2+
Maternal asthma:        
No 92.0 91.0 92.2 97.6 495.6(1) 96.2(1) 409.1(1)
Yes 8.0 9.0 7.8 2.4 0.0001 <0.0001 0.0001
Total 100 100 100 100    
Year of birth:        
1970-1974 18.9 4.1 21.1 27.9 200.4(3) 497.9 (3) 94.1(3)
1975-1979 21.7 7.7 23.8 22.7 <0.0001 <0.0001 0.0001
1980-1984 28.4 23.2 29.2 24.2    
1985-1989 31.0 65.0 25.8 25.2    
Total 100 100 100 100    
Maternal age:        
14-24 37.3 38.5 37.1 34.8 11.8(2) 4.0 (2) 10.2(2)
25-34 55.0 55.3 54.9 57.6 0.003 0.14 0.006
35-49 7.7 6.2 8.0 7.6    
Total 100 100 100 100    
Social class:        
I + II 30.2 29.7 30.2 35.9 48.6(2) 7.4(2) 41.5(2)
III 48.2 48.1 48.2 45.5 <0.0001 0.025 0.0001
IV + V 21.6 22.2 21.6 18.6    
Total 100 100 100 100    
Marital status:        
Married 88.0 79.4 89.4 90.4 25.3(1) 74.0(1) 4.3(1)
Not married 12.0 20.6 10.6 9.6 <0.0001 0.0001 0.04
Total 100 100 100 100    
Parity of mother:        
0 40.5 35.5 41.2 42.0 14.0(4) 24.2(4) 4.65(4)
1 35.4 35.3 35.3 35.9 0.007 <0.0001 0.33
2 15.3 16.8 15.1 14.5    
3 5.9 8.6 5.5 4.9    
4+ 2.9 3.6 2.9 2.7    
Total 100 100 100 100    
Maternal smoking:        
No 71.7 63.3 73.4 76.5 34.9(1) 46.0(1) 11.7(1)
Yes 28.3 36.7 26.6 23.5 0.0001 0.0001 0.0006
Total 100 100 100 100    
Gestational age (wks):        
24-37 12.8 18.0 12.1 10.1 43.2(3) 33.2 (2) 13.3(2)
38-41 77.4 70.7 78.3 80.4 0.0001 0.0001 0.001
42-47 9.8 11.3 9.6 9.5    
Total 100 100 100 100    
Birth weight:        
1000-2999 27.1 32.0 26.3 23.6 27.4(2) 22.5 (2) 16.1(2)
3000-3999 64.4 61.8 64.8 67.9 0.0001 0.0001 0.0003
4000-5499 8.5 6.2 8.9 8.5    
Total 100 100 100 100    
Caesarean delivery:        
No 91.0 89.8 91.2 92.6 14.1(1) 5.7(1) 9.7(1)
Yes 9.0 10.2 8.8 7.4 0.0002 0.02 0.002
Total 100 100 100 100    
Forceps delivery:        
No 88.2 93.4 87.4 86.9 5.9(1) 18.5(1) 1.0(1)
Yes 11.8 6.6 12.6 13.1 0.01 0.0001 0.33
Total 100 100 100 100    
Apgar 1:        
1-5 8.4 9.3 8.2 9.5 9.4(2) 2.1(2) 8.5(2)
6-8 30.3 31.3 30.2 28.48 0.01 0.35 0.01
9-10 96.1 59.4 61.6 62.5    
Total 100 100 100 100    
Number of babies in birth delivery:        
Singleton 98.1 97.6 98.2 97.8 1.7(1) 0.2(1) 2.9(1)
Multiple birth 1.9 2.4 1.8 2.2 0.19 0.68 0.09
Total 100 100 100 100    
Sex of baby:        
Female 32.4 30.1 38.5 48.8 205.9(1) 74.6(1) 145.5
Male 67.4 69.9 61.5 51.2 <0.0001 0.0001 0.0001
Total 100 100 100 100    
Breastfed or not:        
Not breastfed 32.6 41.6 30.9 30.2 8.1(1) 29.7(1) 0.6(1)
Breastfed 67.4 58.4 69.1 69.8 0.004 0.0001 0.46
Total 100 100 100 100    
  1. Missing values: maternal asthma none missing; year of birth none; mother's age 7 (0.2% of cases; social class 869 (27.6%*); marital status 8 (0.2%); parity 2 (0.05%); maternal smoking 1278 (31.8%*); gestational age 558 (13.9%); birth weight 114 (2.8%); caesarean section 114 (2.8%); forceps 114 (2.8%); Apgar 1 1164 (29.0%*); number of babies none missing; sex none; breastfeeding 961 (23.9%*). * = data item not collected in the first five years covered by the study. Numbers on which the percentages are based are given in additional files (see Additional file 1).
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