Acute Impact of Hourly Ambient Air Pollution on Preterm Birth

http://dx.doi.org/10.1289/EHP200



Table 5. Risks of preterm birth at 75th and 95th percentiles of air pollution against the minimum preterm birth concentration of air pollution (threshold) by level of demographic factors.
Factors NO2
[OR (95% CI)]
SO2
[OR (95% CI)]
CO
[OR (95% CI)]
Abbreviations: CI, confidence interval; CO, carbon monoxide (mean of 0–24 hr preceding onset of labor); NO2, nitrogen dioxide (mean of 0–24 hr preceding onset of labor); OR, odds ratio; SO2, sulfur dioxide (mean of 24–48 hr preceding onset of labor). p-Values for differences are presented in Table S3.
Maternal age (years)
< 35
75th vs. threshold 1.00 (0.99, 1.01) 1.06 (0.95, 1.17) 1.12 (0.94, 1.33)
95th vs. threshold 1.26 (1.09, 1.47) 1.01 (0.97, 1.05) 1.30 (1.05, 1.61)
≥ 35
75th vs. threshold 1.01 (0.97, 1.06) 1.03 (0.98, 1.08) 1.09 (0.99, 1.20)
95th vs. threshold 1.14 (1.03, 1.27) 1.02 (0.99, 1.05) 1.14 (1.01, 1.30)
Prepregnancy medical conditions
No
75th vs. threshold 1.01 (0.99, 1.02) 1.04 (0.99, 1.10) 1.12 (1.02, 1.24)
95th vs. threshold 1.18 (1.07, 1.30) 1.01 (0.99, 1.03) 1.24 (1.09, 1.41)
Yes
75th vs. threshold 1.67 (1.07, 2.61) 1.02 (0.95, 1.10) 1.11 (0.47, 2.59)
95th vs. threshold 1.90 (1.18, 3.04) 1.03 (0.97, 1.09) 1.11 (0.51, 2.40)
Previous pregnancy
0
75th vs. threshold 1.00 (0.99, 1.01) 1.10 (1.00, 1.22) 1.02 (0.93, 1.13)
95th vs. threshold 1.06 (0.93, 1.21) 1.00 (0.99, 1.01) 1.09 (0.93, 1.26)
≥ 1
75th vs. threshold 1.01 (0.99, 1.04) 1.01 (0.97, 1.05) 1.15 (1.03, 1.29)
95th vs. threshold 1.24 (1.12, 1.37) 1.03 (0.99, 1.08) 1.25 (1.09, 1.44)
Smoking
Yes
75th vs. threshold 2.02 (1.05, 3.89) 1.08 (0.95, 1.24) 2.35 (0.58, 9.63)
95th vs. threshold 2.59 (1.28, 5.25) 1.04 (0.97, 1.11) 2.47 (0.69, 8.82)
No
75th vs. threshold 1.01 (0.99, 1.03) 1.03 (0.98, 1.08) 1.06 (0.98, 1.15)
95th vs. threshold 1.16 (1.06, 1.27) 1.01 (0.99, 1.04) 1.15 (1.03, 1.28)
Number of births
Single
75th vs. threshold 1.00 (0.99, 1.01) 1.07 (0.99, 1.15) 1.09 (0.98, 1.21)
95th vs. threshold 1.12 (1.02, 1.23) 1.00 (1.00, 1.00) 1.14 (1.00, 1.30)
Multiple
75th vs. threshold 1.03 (0.96, 1.10) 1.01 (0.97, 1.04) 1.11 (0.95, 1.28)
95th vs. threshold 1.32 (1.12, 1.55) 1.10 (1.01, 1.19) 1.28 (1.06, 1.55)
Infant sex
Female
75th vs. threshold 1.01 (0.98, 1.05) 1.01 (0.96, 1.05) 1.16 (1.00, 1.34)
95th vs. threshold 1.20 (1.06, 1.36) 1.02 (0.97, 1.08) 1.26 (1.06, 1.49)
Male
75th vs. threshold 1.00 (0.99, 1.02) 1.07 (1.00, 1.14) 1.06 (0.96, 1.17)
95th vs. threshold 1.15 (1.03, 1.28) 1.01 (0.99, 1.04) 1.14 (1.00, 1.30)
SES index
Index 1–5
75th vs. threshold 1.02 (0.99, 1.05) 1.05 (0.95, 1.17) 3.25 (1.72, 6.15)
95th vs. threshold 1.19 (0.96, 1.46) 1.05 (0.98, 1.13) 3.27 (1.70, 6.27)
Index 6–10
75th vs. threshold 1.01 (0.99, 1.04) 1.03 (0.98, 1.09) 1.08 (0.99, 1.17)
95th vs. threshold 1.18 (1.07, 1.29) 1.01 (0.99, 1.03) 1.17 (1.05, 1.30)