Ahmed SM, et al. – Given that arsenic crosses the placenta—which may adversely affect reproductive outcomes—researchers investigated the relationship between maternal arsenic exposure and fetal/neonatal survival in this prospective cohort involving 1,616 maternal-infant pairs who recruited at ≤ 16 weeks gestational age in Bangladesh (2008-2011). At enrollment, maternal drinking water was tested for arsenic concentration. The time-varying link between maternal arsenic exposure and fetal/neonatal death (all mortality between enrollment and one month after birth) was estimated by using extended Cox regression (both time-dependent coefficients and step functions). They found that higher arsenic exposure was related to a slightly increased mortality rate through the second trimester, and then switched directions around 32 weeks gestation. They also observed a non-linear link that was suggestive of a possible survival pressure of arsenic on developing fetuses, which may also be suggestive of variability in arsenic toxicity by fetal developmental stage.