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. 2011 Apr 12;11:225. doi: 10.1186/1471-2458-11-225

Table 1.

Characteristics of the study population of the original dataset and the imputed datasets.

Baseline population
Original data
Baseline population
Imputed data
% N % (n = 3,963)

Maternal educational level 3,807
Low 23.5 23.8
Intermediate 41.6 41.7
High 35.0 34.5
Sex 3,963
Female 48.1 48.1
Male 51.9 51.9
Older sibling(s) 3,937
Yes 50.7 50.6
No 49.4 49.4
Maternal smoking during pregnancya 3,904
Yes 17.8 17.9
No 82.2 82.1
Breastfeeding duration 3,896
No breastfeeding 17.9 18.0
1-16 weeks 49.6 49.7
>16 weeks 32.5 32.3
Smoking in the home 3,935
Yesb 28.7 28.7
No 71.3 71.3
Day-care centre attendance 3,796
>= 4 hours per week 24.4 24.2
<4 hours per week 75.6 75.9
Eczema at age 8 16.0 3,233 16.4
Asthma symptoms at age 8 13.0 3,308 13.8
Poor general health at age 8 24.6 3,229 26.0
Freq. respiratory infections at age 8 3.9 3,247 4.3
Overweight at age 8c 11.6 2,607 12.0
Obesity at age 8 2.0 2,607 2.3

Mean/SDd Mean/SDd

Maternal age (years) 30.3/3.9 3,920 30.3/3.9
Birthweight child (grams) 3,507/546 3,914 3,507/546

a smoking by the mother during at least the first four weeks of pregnancy

b smoking by anyone in the home more than once a week

c overweight includes obesity

d standard deviation