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Table 1 Demographics of individuals in study population by preterm status (n (%))

From: The associations between environmental quality and preterm birth in the United States, 2000–2005: a cross-sectional analysis

Characteristic Preterm Term
Total 2,335,880 (10) 20,369,188 (90)
Maternal race   
 White, non-Hispanic 1,139,435 (49) 11,719,095 (58)
 Black, non-Hispanic 524,453 (22) 2,771,770 (14)
 Hispanic 524,477 (22) 4,462,084 (22)
 Other 128,440 (5) 1,239,083 (6)
 Missing 19,075 (1) 177,156 (1)
Marital status   
 Married 1,308,539 (56) 13,482,654 (66)
 Unmarried 1,027,341 (44) 6,886,534 (34)
Maternal age   
  < 20 335,318 (14) 2,213,480 (11)
 20–29 1,186,750 (51) 10,700,735 (53)
 30–39 744,495 (32) 6,982,810 (34)
  > 39 69,317 (3) 472,163 (2)
Maternal education   
  < HS 613,828 (26) 4,295,592 (21)
 HS 761,100 (33) 6,145,251 (30)
  > HS 923,370 (40) 9,665,601 (47)
 Missing 37,582 (2) 262,744 (1)
Rural–urban stratum   
 Metropolitan urbanized 1,956,542 (84) 17,214,809 (85)
 Nonmetropolitan urbanized 156,155 (7) 1,320,384 (6)
 Less urbanized 179,568 (8) 1,469,263 (7)
 Thinly populated/rural 33,138 (1) 279,532 (1)