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Table 1 Characteristics of eligible case and control infants in the cohort

From: Association between arsenic, cadmium, manganese, and lead levels in private wells and birth defects prevalence in North Carolina: a semi-ecologic study

Characteristic Case infants (n = 20,151) Mean ± SD   Control infants (n = 668,381) Mean ± SD  
Maternal age at delivery 26.8 ± 6.2   26.9 ± 6.1  
Missing 0   3  
  n (%) n (%)
Maternal race/ethnicity     
 Non-Hispanic White 11,658 (57.9) 381,262 (57.0)
 Non-Hispanic Black 4,751 (23.6) 152,370 (22.8)
 Hispanic 2,976 (14.8) 106,003 (15.9)
 Othera 745 (3.7) 28,009 (4.2)
Missing 21 (<0.1) 737 (<0.1)
Maternal educationb     
 < High school 5,035 (25.0) 151,732 (22.7)
 High school 5,934 (29.4) 190,393 (28.5)
 > High school 9,125 (45.3) 324,228 (48.5)
Missing 57 (0.3) 2,028 (0.3)
Infant sex     
 Female 7,684 (38.1) 327,520 (49.0)
 Male 12,463 (61.8) 340,858 (51.0)
Missing 4 (0.2) 3 (<0.1)
  1. aOther race/ethnicity included individuals reporting Asian, and Pacific Islander/Native American race.
  2. bHighest year of education completed.