Maternal whole blood mercury, cadmium and lead concentrations during pregnancy and lactation and infant heavy metal status at six months

Exposure to mercury (Hg), cadmium (Cd) and lead (Pb) in early life is associated with negative health effects. Pregnancy and lactation are particularly sensitive periods as stored maternal body burdens may be mobilized and transported to the child over placenta and in breast milk. The objective of the study was to evaluate relations between maternal and infant whole blood concentrations of Hg, Cd and Pb in a longitudinal study from pregnancy week 18 to 6 months postpartum. Whole blood Hg, Cd and Pb were measured in pregnancy week 18, 28 and 36, as well as 6 weeks, 4 and 6 months postpartum in 114 Norwegian pregnant and lactating women and their infants at age 6 months. Data on maternal nutrition and lifestyle factors, and months of exclusive breastfeeding were collected. Maternal whole blood Hg and Pb during pregnancy and postpartum were significant positive predictors for whole blood Hg and Pb in infants at six months, while no associations were observed for whole blood Cd. The majority of the infants were breastfed with a mean duration of exclusive breastfeeding of 3.8 (SD 1.5) months. Despite a substantial increase in maternal whole blood Hg, Cd and Pb concentrations postpartum, no associations were seen between infant heavy metal status and months of exclusive breastfeeding, indicating that placental transfer may be the major source of early life exposure to Hg and Pb. Public health interventions should focus on reducing the exposure of heavy metals to females from a very young age.