Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado

http://dx.doi.org/10.1289/ehp.1306722



Table 1. Study population characteristics for unexposed and exposed subjects from rural Colorado 1996–2009.
Maternal or infant characteristic Total Referent group
(0 wells within 10 miles)
Low
(first tertile)a
Medium
(second tertile)a
High
(third tertile)a
aFirst tertile, 1–3.62 wells/mile; second tertile, 3.63–125 wells/mile; third tertile, 126–1,400 wells/mile. bIncludes both Non-Hispanic and Hispanic white. cDuring pregnancy.
Total n (%) 124,842 66,626 (53) 19,214 (15) 19,209 (15) 19,793 (16)
Median 27 27 26 27 27
25th percentile 22 22 21 22 23
75th percentile 32 32 30 31 31
Maternal ethnicity (%)b          
Non-Hispanic white 73 74 72 76 69
Sex (%)          
Male 51 51 51 51 51
Maternal smoking (%)c          
Smokers 11 11 14 13 8
Maternal alcohol (%)c          
No 99 98 99 99 99
Parity (%)          
0 33 33 31 32 32
1 23 23 24 24 25
2 19 19 20 19 20
> 2 25 25 26 25 24
Residential elevation (feet)          
Median 5,000–5,999 6,000–6,999 < 5,000 5,000–5,999 < 5,000
25th percentile < 5,000 5,000–5,999 < 5,000 < 5,000 < 5,000
75th percentile 7,000–7,999 7,000–7,999 5,000–5,999 6,000–6,999 5,000–5,999
Maternal education (%)          
< 12 years 21 20 26 19 22
12 years 30 30 33 29 28
13–15 years 23 22 25 25 24
≥ 16 years 26 28 18 26 27