Table 3. Role of Maternal Folate Status in the Association Between Maternal RBC Lead Levels and Child BMI z Scores and Child OWO Risk (Age Range, 2-15 Years) Stratified by Maternal OWO Statusa.
| Maternal RBC Lead Level, μg/dL | Maternal Folate | Mother-Child Dyad, No. | Child BMI z Score | Child OWO | ||||
|---|---|---|---|---|---|---|---|---|
| Mean (SD) | β (SE) | P Value | Child OWO, No. (%) | OR (95% CI) | P Value | |||
| Non-OWO mothers (n = 565) | ||||||||
| <2.0 | Low | 36 | 0.20 (1.23) | 1 [Reference] | NA | 10 (27.8) | 1 [Reference] | NA |
| <2.0 | Adequate | 178 | 0.23 (1.19) | 0.03 (0.22) | .89 | 44 (24.7) | 0.86 (0.35-2.09) | .74 |
| ≥2.0 | Low | 86 | 0.56 (1.30) | 1 [Reference] | NA | 33 (38.4) | 1 [Reference] | NA |
| ≥2.0 | Adequate | 265 | 0.52 (1.18) | −0.01 (0.15) | .95 | 91 (34.3) | 0.88 (0.51-1.51) | .64 |
| OWO mothers (n = 644) | ||||||||
| <2.0 | Low | 37 | 0.94 (1.22) | 1 [Reference] | NA | 18 (48.6) | 1 [Reference] | NA |
| <2.0 | Adequate | 161 | 0.97 (1.27) | 0.08 (0.21) | .72 | 82 (50.9) | 1.15 (0.52-2.51) | .73 |
| ≥2.0 | Low | 100 | 1.29 (1.12) | 1 [Reference] | NA | 63 (63.0) | 1 [Reference] | NA |
| ≥2.0 | Adequate | 346 | 0.97 (1.10) | −0.31 (0.13) | .02 | 175 (50.6) | 0.59 (0.36-0.95) | .03 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); NA, not applicable; OR, odds ratio; OWO, overweight or obesity; RBC, red blood cell.
SI conversion factor: To convert lead level to micromoles per liter, multiply by 0.0483.
Maternal OWO was defined as a BMI of 25 or higher. Analyses were restricted to those with available folate levels (n = 1209). Low folate status was defined as plasma folate levels of less than 20.4 nmol/L. Adequate folate status was defined as plasma folate levels of at least 20.4 nmol/L. Analyses were performed by linear and logistic regression models for outcome child BMI z scores and child OWO, respectively. Adjusted for maternal educational level, race/ethnicity, smoking status, parity, diabetes, hypertensive disorder, preterm birth, fetal growth, breastfeeding, and child early childhood blood lead level. Among OWO mothers, P values for the interaction between maternal RBC lead levels and maternal folate status were .07 for child BMI z scores and .17 for child OWO.