Association Of Breastfeeding On Infant Lead Exposure In The First Year Of Life In A Mexican Population Of Mother-Infant Pairs

Abstract

Introduction: Bone lead and breastfeeding intensity are important predictors of maternal blood lead levels (MBLLs). There is concern about potential for infant breastfeeding exposure though limited data exist to quantify effects over time. Methods: We quantified effects of breastfeeding on infant BLLs among 360 mother-infant pairs in the Early Life Exposures in Mexico to ENvironmental Toxicants (ELEMENT) birth cohort study. We measured maternal and infant BLLs and breastfeeding status at four times (0, 3, 6, 12 months postpartum). The effect of breastfeeding on infant BLLs was estimated with a linear mixed effect model with a saturated three-way interaction to estimate effects of breastfeeding by time and MBLL adjusting for: maternal age, education years, infant date of birth, and time-varying covariates (infant weight, breastfeeding, MBLL). Results: Breastfeeding (%) at 3, 6, and 12 months was: 81.8, 61.6 and 30.1. Mean±SD BLLs (µg/dL) at each postpartum visit for mothers and infants, respectively, were: 8.2±4.5, 7.4±4.2, 6.2±4.1 and 3.7±2.9, 4.1±2.7, 4.9±3.2. Breastfeeding was associated with an overall increase in infant BLL of 2.9 (1.5, 4.2) µg/dL; this association varied over time and by MBLL. Comparing breastfeeding to non-breastfeeding infants, and adjusting for cord lead, mean difference (95% CI) in BLLs was: 0.6 (-0.3, 1.5) and 0.04 (-1.8, 1.9) µg/dL at 3 and 6 months, respectively. By 12 months, mean difference (95% CI) for MBLL