Table 1

Description of variables in analytic sample, Santiago, Chile, 2004
Continuous Birth Outcome Variable
 N
 Mean
 SD
 Min
 Max
Weeks of gestational age at birth
 56868
 38.62
 1.80
 20
 43
Weight at birth in grams
 56900
 3344.96
 529.01
 508
 6060
Length at birth in cm
 56873
 49.54
 2.51
 30
 61
Maternal Age at birth (years)
 56965
 27.86
 6.68
 11
 51
Maternal Years of Education
 56966
 12.31
 3.37
 0
 22






Continuous Census District Variable
 N
 Mean
 SD
 Min
 Max
Number of domiciles per capita
 56963
 0.27
 0.06
 0.09
 0.73
% domiciles connected to sewer
 56963
 25.17
 3.92
 8.03
 50.16
ln(average total valuation/m2)
 56900
 10.78
 0.88
 8.16
 14.88
% population non-indigenous
 56963
 96.65
 1.58
 90.71
 99.32
% population with formal schooling
 56963
 98.64
 0.67
 95.99
 99.88
% not unemployed and seeking work
 56963
 95.42
 0.99
 92.36
 99.02
% population owners or employers
 56963
 1.91
 1.19
 0.15
 9.78
% domiciles with concrete paving
 56963
 2.19
 4.94
 0.00
 30.43
% domiciles with indoor plumbing
 56963
 25.20
 3.91
 8.03
 50.16
% domiciles with indoor heating.
 56963
 21.22
 4.84
 6.52
 36.03






Census District SES Score1
 56894
 0.00
 1.00
 -2.15
 4.70








In Full Sample
Ages 20+ Only2
Categorical Birth Outcome Variable
 N
 %
N
 %
Male Sex of Newborn
 56970
 51.05
49771
 51.19
Medical Attention at Birth
 56970
 99.96
49771
 99.96
Mother Married at time of Birth
 56970
 53.31
49771
 47.60
Preterm Deliver (< 37 wks)
 56868
 6.41
49674
 6.29
Low Birth Weight (< 2500 g)
 56900
 4.94
49707
 4.80
Preterm LBW (< 2500 g, <37 wks)
 56802
 3.33
49613
 3.27
Very Low Birth Weight (< 1500 g)
 56900
 0.86
49707
 0.86

1 based on principal components analysis of 10 census items

2 for comparison with Figure 1

Kaufman et al. BMC Pregnancy and Childbirth 2008 8:46   doi:10.1186/1471-2393-8-46