Table 1. Characteristics of 1442 Mother-Child Pairs Included in the Study.
| Characteristic | Maternal RBC Lead Level, No. (%) | P for Trend | ||
|---|---|---|---|---|
| <2.0 μg/dL | 2.0 to <5.0 μg/dL | ≥5.0 μg/dL | ||
| Maternal | ||||
| No. | 513 (35.6) | 700 (48.5) | 229 (15.9) | NA |
| Maternal age, mean (SD), y | 26.3 (6.0) | 29.5 (6.5) | 31.0 (5.8) | <.001 |
| Educational level | ||||
| ≤High school | 328 (63.9) | 464 (66.3) | 144 (62.9) | .98 |
| ≥College | 185 (36.1) | 236 (33.7) | 85 (37.1) | |
| Race/ethnicity | ||||
| Black | 269 (52.4) | 496 (70.9) | 202 (88.2) | <.001 |
| Hispanic | 164 (32.0) | 115 (16.4) | 12 (5.2) | |
| Other | 80 (15.6) | 89 (12.7) | 15 (6.6) | |
| Smoking status | ||||
| Nonsmoker | 413 (80.5) | 564 (80.6) | 215 (93.9) | <.001 |
| Smoker | 100 (19.5) | 136 (19.4) | 14 (6.1) | |
| Parity | ||||
| Nulliparous | 246 (48.0) | 266 (38.0) | 90 (39.3) | .004 |
| Multiparous | 267 (52.0) | 434 (62.0) | 139 (60.7) | |
| Prepregnancy BMI category | ||||
| Non-OWO mothers, BMI <25 | 261 (50.9) | 320 (45.7) | 100 (43.7) | .04 |
| OWO mothers, BMI ≥25 | 252 (49.1) | 380 (54.3) | 129 (56.3) | |
| Gestational or preexisting diabetes | 52 (10.1) | 98 (14.0) | 34 (14.8) | .04 |
| Hypertensive disorder | 71 (13.8) | 115 (16.4) | 30 (13.1) | .87 |
| Cesarean delivery | 186 (36.3) | 257 (36.7) | 78 (34.1) | .67 |
| Maternal plasma folate level, nmol/L (95% CI)a | 32.7 (31.0-34.4) | 30.5 (29.1-31.9) | 29.9 (27.6-32.4) | .04 |
| Child | ||||
| Age, median (IQR), y | 7.4 (5.5-9.9) | 8.6 (6.0-10.6) | 9.1 (6.7-11.0) | <.001 |
| Sex | ||||
| Male | 265 (51.7) | 353 (50.4) | 104 (45.4) | .15 |
| Female | 248 (48.3) | 347 (49.6) | 125 (54.6) | |
| Preterm birth | 141 (27.5) | 162 (23.1) | 45 (19.7) | .01 |
| Fetal growth | ||||
| AGA | 412 (80.3) | 539 (77.0) | 185 (80.8) | .46 |
| SGA | 53 (10.3) | 81 (11.6) | 17 (7.4) | |
| LGA | 48 (9.4) | 80 (11.4) | 27 (11.8) | |
| Breastfeeding status | ||||
| Formula exclusively | 131 (25.5) | 178 (25.4) | 47 (20.5) | .37 |
| Both formula and breastfed | 342 (66.7) | 455 (65.0) | 167 (72.9) | |
| Breastfed exclusively | 40 (7.8) | 67 (9.6) | 15 (6.6) | |
| OWO | 191 (37.2) | 311 (44.4) | 110 (48.0) | .002 |
| Postnatal lead level, μg/dL (95% CI)a | 1.8 (1.7-1.8) | 1.9 (1.9-2.0) | 2.1 (2.0-2.3) | <.001 |
Abbreviations: AGA, appropriate for gestational age; BMI, body mass index (calculated as prepregnancy weight in kilograms divided by height in meters squared); IQR, interquartile range; LGA, large for gestational age; NA, not applicable; OWO, overweight or obesity; RBC, red blood cell; SGA, small for gestational age.
SI conversion factors: To convert lead level to micromoles per liter, multiply by 0.0483; folate level to nanomoles per liter, multiply by 2.266.
a
Data are presented as the geometric mean (n = 1201).