Risk of PROM associated with the levels of Pb in maternal urine, stratified by parity
| Pb levels* (μg/g creatinine) | Primiparous (n=6159) | Multiparous (n=1131) | P for interaction | ||||
| N | OR† (95% CI) | OR‡ (95% CI) | N | OR† (95% CI) | OR‡(95% CI) | ||
| T1 | 220 | 1.00 | 1.00 | 20 | 1.00 | 1.00 | <0.01 |
| T2 | 268 | 1.25 (1.04 to 1.51) | 1.24 (1.03 to 1.50) | 24 | 1.21 (0.66 to 2.23) | 1.21 (0.65 to 2.25) | |
| T3 | 318 | 1.52 (1.27 to 1.83) | 1.52 (1.27 to 1.83) | 31 | 1.59 (0.89 to 2.84) | 1.57 (0.87 to 2.83) | |
| P for trend | <0.01 | <0.01 | 0.11 | 0.13 | |||
*Pb levels: primiparous, T1 (<2.66), T2 (2.66–4.71), T3 (≥4.71); multiparous, T1 (<2.61), T2 (2.61–4.61), T3 (≥4.61).
↵†Unadjusted OR.
↵‡Adjusted for maternal age, family income, pre-BMI, passive smoking and pregnancy-induced hypertension.
BMI, body mass index; Pb, lead; PROM, premature rupture of membranes; T, tertile.