Maternal Blood Metal levels in Association with Birth Outcomes in Northern Puerto Rico

Abstract

PDS 74: Pregnancy outcomes, Exhibition Hall (PDS), Ground floor, August 26, 2019, 1:30 PM - 3:00 PM Background: In previous studies exposures to heavy metals such as Pb and Cd have been associated with adverse birth outcomes; however, knowledge of effects at low levels of exposure and of other elements remain limited. Methods: We examined individual and mixture effects of 10 metals on birth outcomes among 810 pregnant women in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) cohort. We measured As, Cd, Co, Cs, Cu, Mn, Hg, Ni, Pb, and Zn in maternal blood collected at 16–20 and 24–28 weeks gestation. We used linear and logistic regression to independently examine associations between geometric mean (GM) concentrations of each metal across visits and 1) gestational age and birthweight z-scores; and 2) preterm birth and small for gestational age (SGA). We evaluated effect modification with infant sex*metal interaction terms. To identify critical windows of susceptibility, birth outcomes were regressed on visit-specific metal concentrations. We used elastic net (ENET) regularization to identify individual metals most critical to each outcome, accounting for correlated exposures. Results: In adjusted models, an interquartile range increase in GM Pb was associated with 1.70 higher odds of preterm birth (95%CI: 1.24, 2.34) and 24% shorter gestational age (95%CI:-36.7%, -8.6). Mn and Zn were also associated with higher odds of preterm birth and shorter gestational age, although only significant among the highest tertile and females, respectively. Co, Cs, and Ni measured later in pregnancy were positively associated with birthweight z-score, and Ni was associated with decreased odds of SGA. ENET yielded similar results. Conclusions: As the PROTECT cohort has lower Pb concentrations (GM=0.33 ug/dL) compared to the mainland US, our findings suggest that low-level prenatal lead exposure, as well as higher Mn and Zn exposure, may adversely affect birth outcomes. Higher concentrations of certain essential metals later in pregnancy were associated with increased size at birth.