DECREASE IN BIRTH-WEIGHT IN RELATION TO MATERNAL BONE-LEAD BURDEN

Objectives. Birth weight predicts infant survival, growth, and develop ment. Previous research suggests that low levels of fetal lead exposur e, as estimated by umbilical cord blood-lead levels at birth, may have an adverse effect on birth weight. This report examines the relations hip of lead levels in cord blood and maternal bone to birth weight. Me thods. Umbilical cord and maternal venous blood samples and anthropome tric and sociodemographic data were obtained at delivery and 1-month p ostpartum. Blood-lead levels were analyzed by atomic absorption spectr ophotometry. Maternal tibia and patella lead levels were determined at 1-month postpartum with use of a spot-source Cd-109 K-X-ray fluoresce nce instrument. The relationship between birth weight and lead burden was evaluated by multiple regression with control of known determinant s of size at birth. Results. Data on all variables of interest were ob tained for 272 mother-infant pairs. After adjustment for other determi nants of birth weight, tibia lead was the only lead biomarker clearly related to birth weight. The decline in birth weight associated to inc rements in tibia lead was nonlinear and accelerated at the highest tib ia lead quartile. In the upper quartile, neonates were on average, 156 grams lighter than those in the lowest quartile. Other significant bi rth weight predictors included maternal nutritional status, parity, ed ucation, gestational age, and smoking during pregnancy. Conclusions. O ur results indicate that bone-lead burden is inversely related to birt h weight. Taken together with other research indicating that lead can mobilize from bone into plasma without detectable changes in whole blo od lead, these findings suggest that bone lead might be a better bioma rker than blood lead. Because lead remains in bone for years to decade s, mobilization of bone lead during pregnancy may pose a significant f etal exposure with health consequences, long after maternal external l ead exposure has declined.