Basic characteristics and urinary Pb concentrations (μg/g creatinine) of the 7290 pregnant women
| Characteristics | N (%) | Median (IQR) | P values |
| Pb (μg/g creatinine) | |||
| Total | 7290 | 3.44 (2.30–5.64) | |
| Maternal age (years) | 0.43 | ||
| <25 | 805 (11.0) | 3.37 (2.27–5.52) | |
| 25–29 | 3985 (54.7) | 3.49 (2.32–5.77) | |
| 30–34 | 2011 (27.6) | 3.40 (2.29–5.47) | |
| ≥35 | 489 (6.7) | 3.41 (2.15–5.94) | |
| Education background (years) | 0.63 | ||
| ≤9 | 1001 (13.7) | 3.45 (2.40–5.63) | |
| 9–12 | 1389 (19.1) | 3.47 (2.35–5.56) | |
| >12 | 4898 (67.2) | 3.42 (2.26–5.66) | |
| Missing | 2 (0.03) | 5.69 (3.50–7.90) | |
| Family income(¥/year) | 0.37 | ||
| <50 000 | 3021 (41.4) | 3.52 (2.31–5.75) | |
| ≥50 000 | 4148 (56.9) | 3.39 (2.28–5.60) | |
| Missing | 121 (1.7) | 3.50 (2.38–5.83) | |
| Parity | 0.43 | ||
| primiparous | 6159 (84.5) | 3.45 (2.30–5.66) | |
| multiparous | 1131 (15.5) | 3.38 (2.26–5.59) | |
| Prepregnancy BMI (kg/m2) | 0.10 | ||
| <18.5 | 1527 (20.9) | 3.47 (2.27–5.77) | |
| 18.5–23.9 | 4832 (66.3) | 3.41 (2.29–5.56) | |
| ≥24 | 910 (12.5) | 3.60 (2.39–6.04) | |
| Missing | 21 (0.3) | 3.87 (2.07–8.12) | |
| Passive smoking during pregnancy | 0.07 | ||
| Yes | 1670 (22.9) | 3.30 (2.29–5.32) | |
| No | 5620 (77.1) | 3.47 (2.30–5.71) | |
| Pregnancy-induced hypertension | 0.08 | ||
| Yes | 286 (3.9) | 3.26 (2.18–5.21) | |
| No | 7004 (96.1) | 3.44 (2.30–5.66) | |
| Gestational age (weeks) | <0.01 | ||
| <37 | 291 (4.0) | 3.99 (2.62–7.54) | |
| ≥37 | 6999 (96.0) | 3.42 (2.29–5.60) | |
| Infant gender | 0.02 | ||
| Male | 3890 (53.4) | 3.48 (2.34–5.78) | |
| Female | 3400 (46.6) | 3.40 (2.25–5.52) | |
| PROM | 881 (12.1) | 3.88 (2.55–6.59) | 0.47 |
| Preterm PROM | 147 (2.0) | 3.96 (2.63–7.67) | |
| Term PROM | 734 (10.1) | 3.87 (2.54–6.34) |
BMI, body mass index; Pb, lead; PROM, premature rupture of membranes.