Prenatal mercury exposure and birth outcomes

Background Results regarding the association between mercury exposure and anthropometry at birth, gestational length and placental weight are inconsistent, as is the role of seafood intake in these associations. Objective We assessed whether prenatal mercury exposure is associated with anthropometry at birth, placental weight and gestational length in a population with a relatively high exposure to mercury from seafood consumption. Methods Total mercury (T–Hg) was determined in cord blood from 1869 newborns with birth outcome measures, within the Spanish multicenter INMA cohort from 2004 to 2008. We adjusted cohort specific linear and Cox regression models to evaluate the association between T–Hg and birth anthropometry (weight, length, and head circumference), placental weight and gestational length. Non-spontaneous labor was taken to be censoring in the survival analysis. Final estimates were obtained using meta-analysis. Results Geometric mean T–Hg was 8.2 μg/L. A doubling of T–Hg was associated with a 7.7 g decrease in placental weight (95% CI: −13.6, −1.8) and marginally with head circumference (beta: −0.052 cm, 95% CI: −0.109, 0.005). T–Hg was also inversely related to weight and length, although with weaker estimates. Mercury exposure was not associated with the length of gestation. The inverse relation between T–Hg and growth was enhanced when the intake of different seafood groups was adjusted for in the models. Conclusions Prenatal mercury exposure may be associated with reduced placental and fetal growth. Confounding by fish intake should be considered when assessing these relationships.