Intrauterine Exposure to Low Levels of Lead: The Status of the Neonate

It has been suggested that lead (Pb) at low exposure levels is a behavioral teratogen. Blood lead (Pb-B) was measured in 185 samples of maternal blood and in 162 samples of cord blood drawn from members of a cohort of mother-infant pairs. Routine newborn assessments, an examination for minor anomalies, the Brazelton Neonatal Behavioral Assessment (NBAS), and part of the Graham/Rosenblith Behavioral Examination (G/R) were administered. Maternal and cord Pb-B correlated 0.80. In regression analyses, Apgar scores, birthweight, length, head circumference, neonatal anomalies, and seven behavioral scales were unrelated to either maternal or cord Pb-B. Three scales--the NBAS Abnormal Reflexes, the G/R Neurological Soft Sign, and the G/R Muscle Tonus Scales--were related minimally to either cord or maternal Pb-B. Because of the contrast in maternal and cord results, despite the high correlation of maternal and cord Pb-B, the data were reanalyzed for 132 cases with paired data. Only the Soft Sign Scale remained significant and that only for cord, but not maternal Pb-B. Regression analysis revealed a suppression with the Soft Sign Scale related to the variance of the cord Pb-B that was not common with maternal Pb-B. The possibility that the fetus under stress tends to accumulate Pb was considered.