A cohort study of the association between prenatal arsenic exposure and age at menarche in a rural area, Bangladesh

•The first study based on individual arsenic exposure data to evaluate age at menarche.•Prenatal arsenic exposure was associated with a menarche delay.•Exposure to more than 50 µg/L of water arsenic implied 2.8 months delay in menarche.•Effects on sexual maturation add to the known consequences of arsenic exposure. Millions of individuals worldwide, particularly in Bangladesh, are exposed to arsenic, mainly through drinking water from tube wells. Arsenic is a reproductive toxicant, but there is limited knowledge of whether it influences pubertal development. We evaluated the association between prenatal arsenic exposure and age at menarche. This prospective study was based on data from two studies conducted in Matlab, Bangladesh—the Maternal and Infant Nutrition Interventions in Matlab (MINIMat) trial and the Health Consequences of Arsenic in Matlab (AsMat) study. We included 809 MINIMat girls who participated in assessing age at menarche from July 2016 to June 2017 and had prenatal arsenic exposure data through the AsMat study via measurements in tube well water used by the mothers during pregnancy. The exposure was categorized into