Table 3.
Logistic regression analyses of the association between maternal urinary chromium (μg/g cr) and preterm birth.
| Chromium | Term Births | Preterm Birth | |||
|---|---|---|---|---|---|
| n | n | ORa(95% CI) | ORb(95% CI) | ORc(95% CI) | |
| Total (n = 7290) | |||||
| Tertile1 (≤1.07) | 2333 | 31 | Reference | Reference | Reference |
| Tertile2 (1.07–3.52) | 2336 | 71 | 2.19(1.43, 3.37) | 2.16(1.40, 3.34) | 1.55(0.99, 2.42) |
| Tertile3 (>3.52) | 2334 | 185 | 5.56(3.75, 8.23) | 5.32(3.56, 7.93) | 1.89(1.13, 3.18) |
| p for trend | <0.01 | <0.01 | <0.01 | ||
| Excluding urine creatinine <0.3 or >3 g/L (n = 5430) | |||||
| Tertile1 (≤0.88) | 1749 | 16 | Reference | Reference | Reference |
| Tertile2 (0.88–2.11) | 1755 | 42 | 2.62(1.46, 4.67) | 2.52(1.41, 4.53) | 2.05(1.13, 3.74) |
| Tertile3 (>2.11) | 1750 | 118 | 7.38(4.31, 12.63) | 6.74(3.91, 11.62) | 3.04(1.58, 5.84) |
| p for trend | <0.01 | <0.01 | <0.01 | ||
| Excluding pregnancy-induced hypertension (n = 7004) | |||||
| Tertile1 (≤1.07) | 2249 | 28 | Reference | Reference | Reference |
| Tertile2 (1.07–3.53) | 2256 | 58 | 2.03(1.28, 3.20) | 2.00(1.27, 3.17) | 1.46(0.91,2.34) |
| Tertile3 (>3.53) | 2249 | 164 | 5.66(3.74, 8.57) | 5.46(3.59, 8.29) | 1.92(1.12, 3.29) |
| p for trend | <0.01 | <0.01 | 0.02 | ||
Abbreviations: CI, confidence interval; OR, odds ratio.
aUnadjusted odds ratio.
bAdjusted for maternal age, educational level, BMI, parity, and pregnancy-induced hypertension.
cAdjusted for maternal age, educational level, BMI, parity, pregnancy-induced hypertension, and other metals.