Effect of maternal lead burden on infant weight and weight gain at one month of age among breastfed infants.

INTRODUCTION

Transfer of lead from bone to the bloodstream increases during lactation. However, the effect of maternal lead burden on growth in breastfed newborns is still unknown. This study examined early postnatal growth in a cohort of healthy breastfed newborns in relation to maternal bone lead burden.

METHODS

Lead levels were measured among 329 mother-infant pairs in umbilical cord blood at birth and in maternal and infant venous blood at 1 month postpartum. Maternal evaluations at 1 month postpartum included lead measures in blood and bone (measured in the tibia and the patella). Blood lead was determined by graphite furnace atomic absorption spectrophotometry. Bone lead was measured by (109)Cd Kx-radiograph fluorescence instrument. The primary endpoints were attained weight 1 month of age, and weight gain from birth to 1 month of age, which were analyzed in relation to lead biomarkers and relevant covariates by linear regression models.

RESULTS

Infants studied had an average weight gain of 33.1 g/day (standard deviation [SD] = 11.6). Mean infant (at 1 month of age) and maternal blood lead levels were 5.6 microg/dL (SD = 3.0) and 9.7 microg/dL (SD = 4.1), respectively. Mean maternal bone lead levels were 10.1 microg of lead/g (SD = 10.3) and 15.29 microg of lead/g (SD = 15.2) of bone mineral for tibia and patella, respectively. Infant blood lead levels were inversely associated with weight gain, with an estimated decline of 15.1 g per microg/dL of blood lead. Children who were exclusively breastfed had significantly higher weight gains; however, this gain decreased significantly with increasing levels of patella lead. The multivariate regression analysis predicted a 3.6-g decrease in weight at 1 month of age per microg of lead per gram bone mineral increase in maternal patella lead levels.

CONCLUSIONS

Maternal lead burden is negatively associated to infant attained weight at 1 month of age and to postnatal weight gain from birth to 1 month of age. Additional studies are needed to better understand this source of exposure and to develop interventions to minimize its impact.