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Table 1 Characteristics at study entry for women residing in North Carolina who delivered at least two singleton neonates, 2002-2006

From: A longitudinal study of exposure to fine particulate matter during pregnancy, small-for-gestational age births, and birthweight percentile for gestational age in a statewide birth cohort

  Non-Hispanic black
(n = 13,797)
n (%)a
Non-Hispanic white
(n = 39,617)
n (%)a
p-valueb
Infants born SGA 2940 (21.3) 2305 (5.82) < 0.001
Mean birthweight percentile for gestational age 37.3 (26.5) 51.3 (27.9)  
Age of mother, years    < 0.001
  < 20 4372 (31.7) 4993 (12.6)  
 20-24 5333 (38.6) 9877 (25.0)  
 25-29 2442 (17.7) 12,015 (30.3)  
 30-34 1248 (9.05) 10,078 (25.4)  
 35-39 373 (2.70) 2514 (6.32)  
 40-44 31 (0.22) 130 (0.33)  
Educational level, years    < 0.001
 No high school diploma 4308 (31.2) 5352 (13.5)  
 High school diploma 7727 (56.0) 17,281 (43.6)  
 College diploma 1762 (12.8) 16,894 (42.9)  
Not married 10,052 (72.9) 8072 (20.4) < 0.001
Birth order    < 0.001
 1 7865 (57.0) 27,584 (69.6)  
 2 4092 (29.7) 8921 (22.5)  
 3 1794 (13.0) 3053 (7.71)  
  > 4 46 (0.33) 59 (0.15)  
Smoker 1412 (10.2) 5491 (13.9) < 0.001
Median household income (census tract) $35,239 (13,115) $46,485 (16,621) < 0.001
  1. aThe cell count and percentage are presented except in the cases of birthweight percentile for gestational age and median household income, where the mean and standard deviation are provided
  2. bThe chi-square test was used to test for differences by race group for categorical variables. The Kruskal-Wallis rank sum test was used birthweight percentile for gestational age and census tract-level median household income