Prenatal mercury exposure and birth weight

•Mercury, a highly toxic metal, can readily cross the placenta as methylmercury and potentially affects the fetus.•Blood mercury of non-occupationally exposure women can exceed the acceptable level (5.8 μg/dL).•Prenatal mercury exposure can reduce birth weight. Adverse effects of prenatal mercury exposure on pregnancy outcomes remain a public health concern. We assessed the relationship between prenatal mercury exposure and newborn anthropometric characteristics in 334 mother-child pairs from the early stages of pregnancy to delivery in Tokyo, Japan, between December 2010 and October 2012. We found a negative correlation between blood mercury levels during the first and second trimesters of gestation and birth weight (r = −0.134 and −0.119, respectively; p