Relation between in Utero Arsenic Exposure and Birth Outcomes in a Cohort of Mothers and Their Newborns from New Hampshire

BACKGROUND: Studies suggest that arsenic exposure influences birth outcomes; however, findings are mixed. OBJECTIVE: We assessed in utero arsenic exposure in relation to birth outcomes and whether maternal prepregnancy weight and infant sex modified the associations. Methods: Among 706 mother-infant pairs exposed to low levels of arsenic through drinking water and diet, we assessed in utero arsenic exposure using maternal second-trimester urinary arsenic, maternal prepregnancy weight through self-report, and birth outcomes from medical records. RESULTS: Median (interquartile range) of total urinary arsenic [tAs; inorganic arsenic (iAs) + monomethyl-arsonic acid (MMA) + dimethylarsinic acid (DMA)] was 3.4 mu g/L (1.7-6.0). In adjusted linear models, each doubling of tAs was associated with a 0.10-cm decrease (95% CI: -0.19, -0.01) in head circumference. Results were similar for MMA and DMA. Ln(tAs) and ln(DMA) were positively associated with birth length in infant males only; among males, each doubling of tAs was associated with a 0.28-cm increase (95% CI: 0.09, 0.46) in birth length (p(interaction) = 0.04). Results were similar for DMA. Additionally, arsenic exposure was inversely related to ponderal index, and associations differed by maternal weight. Each ln(tAs) doubling of tAs was associated with a 0.55-kg/m(3) lower (95% CI: -0.82, -0.28, p < 0.001) ponderal index for infants of overweight/obese, but not normal-weight, mothers (pinteraction < 0.01). Finally, there was a significant inter-action between maternal weight status, infant sex, and arsenic exposure on birth weight (p(interaction) = 0.03). In girls born of overweight/obese mothers, each doubling of tAs was associated with a 62.9-g decrease (95% CI: -111.6, -14.2) in birth weight, though the association was null in the other strata. CONCLUSIONS: Low-level arsenic exposure may affect fetal growth, and the associations may be modified by maternal weight status and infant sex.