Table 2.
Adjusted parameter estimates (95% confidence interval) for the change in birth outcomes with each unit increase in natural log–transformed maternal 2nd trimester urinary arsenic for all participants and by maternal prepregnancy weight status (n = 706).a , b
| Outcome/maternal urinary arsenic variable | Overall (n = 706) | Normal weight (n = 406) | Overweight/obese (n = 300) | p for interactionc |
|---|---|---|---|---|
| Gestational age (weeks)d | ||||
| Ln(iAs) | 0.04 (–0.06, 0.15) | 0.10 (–0.03, 0.23) | –0.04 (–0.20, 0.12) | 0.18 |
| Ln(MMA) | 0.05 (–0.04, 0.14) | 0.08 (–0.03, 0.20) | 0.00 (–0.13, 0.14) | 0.38 |
| Ln(DMA) | 0.09 (–0.03, 0.21) | 0.11 (–0.05, 0.27) | 0.07 (–0.11, 0.26) | 0.78 |
| Ln(tAs) | 0.10 (–0.03, 0.22) | 0.12 (–0.05, 0.28) | 0.07 (–0.11, 0.26) | 0.74 |
| Head circumference (cm)e | ||||
| Ln(iAs) | –0.08 (–0.19, 0.02) | –0.12 (–0.26, 0.02) | –0.04 (–0.21, 0.13) | 0.51 |
| Ln(MMA) | –0.10 (–0.19, –0.01)* | –0.08 (–0.19, 0.04) | –0.14 (–0.28, 0.00)* | 0.49 |
| Ln(DMA) | –0.12 (–0.25, 0.00) | –0.13 (–0.29, 0.04) | –0.11 (–0.30, 0.08) | 0.90 |
| Ln(tAs) | –0.14 (–0.27, –0.01)* | –0.15 (–0.32, 0.02) | –0.12 (–0.31, 0.07) | 0.83 |
| Birth length (cm)e | ||||
| Ln(iAs) | 0.06 (–0.10, 0.22) | 0.01 (–0.20, 0.22) | 0.13 (–0.12, 0.39) | 0.46 |
| Ln(MMA) | 0.10 (–0.04, 0.24) | 0.02 (–0.16, 0.20) | 0.21 (0.00, 0.43) | 0.18 |
| Ln(DMA) | 0.22 (0.03, 0.41)* | 0.09 (–0.16, 0.35) | 0.38 (0.09, 0.67)* | 0.14 |
| Ln(tAs) | 0.21 (0.01, 0.40)* | 0.07 (–0.19, 0.33) | 0.37 (0.08, 0.67)* | 0.12 |
| Birth weight (g)e | ||||
| Ln(iAs) | –9.7 (–38.4, 19.0) | –0.5 (–37.9, 37.0) | –22.9 (–67.6, 21.8) | 0.45 |
| Ln(MMA) | 3.9 (–20.5, 28.3) | 19.4 (–12.4, 51.3) | –18.0 (–55.8, 19.8) | 0.14 |
| Ln(DMA) | 4.1 (–29.5, 37.8) | 24.0 (–20.5, 68.4) | –21.9 (–72.8, 29.0) | 0.18 |
| Ln(tAs) | –1.3 (–35.8, 33.2) | 15.8 (–30.1, 61.8) | –23.1 (–74.9, 28.7) | 0.27 |
| Ponderal index (kg/m3)e | ||||
| Ln(iAs) | –0.17 (–0.39, 0.05) | –0.01 (–0.30, 0.28) | –0.40 (–0.75, –0.06)* | 0.08 |
| Ln(MMA) | –0.13 (–0.32, 0.06) | 0.11 (–0.13, 0.35) | –0.47 (–0.76, –0.19)* | < 0.01 |
| Ln(DMA) | –0.32 (–0.58, –0.06)* | 0.04 (–0.30, 0.38) | –0.79 (–1.18, –0.40)** | < 0.01 |
| Ln(tAs) | –0.34 (–0.60, –0.07)* | 0.02 (–0.33, 0.37) | –0.79 (–1.18, –0.40)** | < 0.01 |
| aNormal weight defined as prepregnancy BMI 18.5–24.9 kg/m2 and overweight/obese defined as prepregnancy BMI ≥ 25 kg/m2; 25 underweight mothers (BMI < 18.5 kg/m2) excluded from analysis. bResults from a series of regression models fitting each birth outcome on each arsenic exposure measure [natural log–transformed inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), total arsenic (iAs + MMA + DMA) (tAs)]; models are adjusted as noted. cp-Value from a two-sided Wald’s t-test testing the significance of a multiplicative term of maternal prepregnancy weight status (categorical) and each arsenic exposure in the regression model. dModel adjusted for maternal age (continuous), education level (ordinal with the five categories listed in Table 1 assigned values of 1–5, respectively), parity (continuous), and infant sex; models for overall sample additionally adjusted for maternal prepregnancy weight status (categorical). eModel adjusted for variables described in footnote d as well as gestational age (continuous). *p < 0.05. **p < 0.001. | ||||