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Table 3 Characteristics of the study population (N = 396,049) according to the categories of exposure, Taiwan, 2001–2003.

From: Water disinfection by-products and the risk of specific birth defects: a population-based cross-sectional study in Taiwan

Characteristic TTHMs (0–4 μg/L) Reference N (%) TTHMs (5–9 μg/L) Low N (%) TTHMs (10–19 μg/L) Medium N (%) TTHMs (20+ μg/L) High N (%) Total N (%)
Total 181,985 (100%) 55,950 (100%) 82,797 (100%) 75,317 (100%) 396,049 (100%)
Gender of infant      
   Male 95,027 (52.2%) 29,128 (52.1%) 43,155 (52.1%) 39,413 (52.3%) 206,723(52.2%)
   Female 86,958 (47.8%) 26,822 (47.9%) 39,642 (47.9%) 35,904 (47.7%) 189,326 (47.8%)
Maternal age      
   <20 years 6,419 (3.5%) 1,838 (3.3%) 3,499 (4.2%) 3,461 (4.6%) 15,217 (3.8%)
   20–34 156,087 (85.8%) 46,871 (83.8%) 72,402 (87.4%) 65,947 (87.6%) 341,307 (86.2%)
   35- 19,476 (10.7%) 7,241 (12.9%) 6,893 (8.3%) 5,909 (7.8%) 39,519 (10.0%)
Maternal diabetes mellitus      
   Yes 418 (0.2%) 189 (0.3%) 179 (0.2%) 144 (0.2%) 930 (0.2%)
   No 181,567 (99.8%) 55,761 (99.7%) 82,618 (99.8%) 75,173 (99.8%) 395,119 (99.8%)
Plurality      
   Singleton 176,791 (97.1%) 54,383 (97.2%) 80,755 (97.5%) 73,442 (97.5%) 385,371 (97.3%)
   Multiple birth 5,194 (2.9%) 1,567 (2.8 %) 2,042 (2.5%) 1,875 (2.5%) 10,678 (2.7%)
Population density (no of people/km2)*      
   <1000 29,881 (16.4%) 6,697 (12.0%) 20,387 (24.6%) 26,392 (35.2%) 83,357 (21.1%)
   1000–5000 71,005 (39.0%) 27,257 (48.7%) 23,569 (28.5%) 31,823 (42.5%) 153,654 (38.8%)
   >5000 81,099 (44.6%) 21,996 (39.3%) 38,841 (46.9%) 16,738 (22.3%) 158,674 (40.1%)