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Table 1 Characteristics of subjects in Liuzhou city, Guangxi Province

From: The association between ambient air pollution and birth defects in five major ethnic groups in Liuzhou, China

Characteristics Infants with BDs
n (%)
Normal infants n (%) χ2 P
Maternal age (years)
  < 20 19(3.0%) 936 (2.9%) 11.10 < 0.01
 20 ~ 73 (11.5%) 4271 (13.4%)   
 25 ~ 191 (30.1%) 10,359 (32.5%)   
 30 ~ 199 (31.3%) 10,517 (33.0%)   
  ≥ 35 153 (24.1%) 5831 (18.3%)   
Family income (RMB per capita)
  < 2000 156 (24.6%) 7662 (23.5%) 2.54 0.16
 2000~ 107 (16.8%) 5087 (15.6%)   
 4000~ 250 (39.4%) 13,147 (40.4%)   
  ≥ 8000~ 123 (19.4%) 6653 (20.4%)   
Maternal education
 Primary or below 28 (4.4%) 128 (0.4%) 9.49 0.00
 Middle school 184 (29.0%) 11,567 (35.5%)   
 High or technical school 124 (19.5%) 10,543 (32.4%)   
 College or above 299 (47.1%) 10,311 (31.7%)   
Birth weight(g)
  < 1500 g 316 (49.8%) 194 (0.6%) 2723.66 < 0.01
 1500 g ~ 52 (8.2%) 1799 (5.6%)   
 2500 g ~ 201 (31.6%) 22,424 (70.3%)   
  ≥ 3500 g 66 (10.4%) 7497 (23.5%)   
Infant gender
 Male 361 (56.8%) 16,790 (52.6%) 14.50 < 0.01
 Female 233 (36.7%) 15,124 (47.4%)   
 Unknown gender 41 (6.5%) 0 (0.0%)   
Number of pregnancies
 1 110 (17.3%) 6591 (20.7%) 1.30 0.25
 2 175 (27.6%) 9130 (28.6%)   
  ≥ 3 350 (55.1%) 16,193 (50.7%)   
Total previous live births
 0 97 (15.3%) 21 (0.1%) 740.78 < 0.01
 1 304 (47.9%) 12,259 (38.4%)   
  ≥ 2 234 (36.8%) 19,634 (61.5%)   
Residence
 Urban 250 (39.4%) 15,510 (48.6%) 15.50 < 0.01
 Rural 385 (60.6%) 16,404 (51.4%)