Table 1

 Distribution of 2.5 year old children in Quebec longitudinal study of child development (QLSCD 1998–2002) according to their characteristics, their neonatal health problems, and their environment during the past 12 months (n = 1946)

%95% CI
*Small for gestational age (<10th centile) according to the Kramer curve 2001. †Coefficient of variation between 15% and 25%; data should be interpreted with caution. The coefficient of variation is a measure of dispersion of the data around the mean. It is the ratio of the standard deviation to the mean of a distribution. It does not have any metric and is usually expressed in percentage. Large coefficients of variation indicate a large dispersion of data around the mean and a loss of accuracy of the mean estimate (BMDP statistical software, Los Angeles, 1990).
Baby’s sex
Female49.447.1 to 51.8
Male50.648.2 to 52.9
Birth rank
1st44.341.9 to 46.6
2nd39.136.9 to 41.4
3rd or more16.614.9 to 18.3
Congenital abnormality
No92.090.7 to 93.3
Yes8.06.7 to 9.3
Small for gestational age <10th centile*
No93.592.3 to 94.7
Yes6.55.3 to 7.7
Premature birth (<37 weeks)
No93.592.1 to 94.8
Yes6.55.2 to 7.9
Parents’ smoking (past 12 months)
No parent smoking65.763.4 to 68.0
One parent who smokes in the home21.319.2 to 23.3
Two parents who smoke in the home13.011.5 to 14.7
Length of exclusive breast feeding
Never breast fed28.226.1 to 30.3
Breast fed since birth, but not exclusively5.84.6 to 6.9
1 day to 4 weeks18.917.0 to 20.8
5–9 weeks20.118.2 to 21.9
10–14 weeks10.59.2 to 11.9
15 weeks or longer16.614.9 to 18.3
Type of child care (past 12 months)
At home with the mother or another person49.647.2 to 51.9
Outside of the home32.430.2 to 34.5
At a day care centre16.815.1 to 18.5
Variable child care1.2†0.8 to 1.8