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. Author manuscript; available in PMC: 2018 Oct 1.
Published in final edited form as: Environ Res. 2017 Jun 9;158:72–81. doi: 10.1016/j.envres.2017.05.030

Table 4.

Odds ratios for preterm birth by quartile of maternal urinary perchlorate concentration in the study population of pregnant women from San Diego County 2000–2003

Both sexes
Males
Females
Gro
up		 Per
c
qua
rt.		 Cas
es		 Co
nt		 O
R1 		95
%
CI
L 		95
%
CI
U 		p-
tre
nd		 Cas
es		 Co
nt		 O
R1 		95
%
CI
L 		95
%
CI
U 		p-
tre
nd		 Cas
es		 Co
nt		 O
R1 		95
%
CI
L 		95
%
CI
U 		p-
tre
nd
All preterm births:
1 36 452 1.00 Ref 21 218 1.00 Ref 15 234 1.00 Ref
2 33 458 0.86 0.51 1.45 17 220 0.77 0.38 1.56 16 238 0.94 0.43 2.04
3 43 447 1.09 0.64 1.85 21 219 0.86 0.41 1.82 22 228 1.30 0.60 2.82
4 46 442 1.11 0.64 1.92 0.72 26 217 1.14 0.53 2.45 0.73 20 225 1.06 0.47 2.38 0.90
Preterm ≥2500 g:
1 19 469 1.00 Ref 9 230 1.00 Ref 10 239 1.00 Ref
2 22 469 1.09 0.56 2.11 12 225 1.39 0.54 3.57 10 244 0.86 0.33 2.22
3 33 457 1.53 0.79 2.99 19 221 1.82 0.69 4.80 14 236 1.22 0.47 3.13
4 37 451 1.84 0.91 3.72 0.09 24 219 3.03 1.09 8.40 0.03 13 232 1.07 0.39 2.89 0.90
Preterm <2500 g:
1 17 471 1.00 Ref 12 227 1.00 Ref 5 244 1.00 Ref
2 11 480 0.62 0.27 1.39 5 232 0.37 0.12 1.12 6 248 1.11 0.30 4.08
3 10 480 0.57 0.23 1.39 2 238 0.16 0.03 0.79 8 242 1.44 0.40 5.21
4 9 479 0.42 0.16 1.06 0.07 2 241 0.12 0.02 0.61 0.01 7 238 1.06 0.28 3.97 0.94

Abbreviations: CIL, lower confidence interval; CIU, upper confidence interval; Cont, controls; OR, odds ratio; Perc quart, maternal urinary perchlorate concentration quartile unadjusted for urinary creatinine concentrations (cut-off points are 3.94, 6.50, and 10.0 µg/L); Ref, Reference category

1

Adjusted for creatinine (log10), maternal age, maternal weight, race, (and sex, for analyses of both sexes)