Variation in blood lead and hematocrit levels during pregnancy in a socioeconomically disadvantaged population.

Lead is a long-recognized human toxicant that crosses the placenta. Fetal sensitivity to environmental agents can vary with stage of development; therefore, how maternal blood lead levels change during pregnancy and how fetal exposure is influenced provide useful knowledge. In this study, the authors describe longitudinal changes in blood lead levels during the course of pregnancy in a sample of socioeconomically disadvantaged pregnant women. The women were recruited early in pregnancy when they sought care at one of two obstetrics clinics in Albany, New York. Maternal blood lead levels changed between the 1st and 2nd trimesters, from 1.99 microg/dl to 1.69 microg/dl (hematocrit corrected, 1.70-1.62); between the 2nd and 3rd trimester from 1.78 microg/dl to 1.86 microg/dl (hematocrit corrected, 1.65-1.72); and between 3rd trimester and delivery from 1.80 microg/dl to 2.17 microg/dl (hematocrit corrected, 1.70-1.86). These changes were statistically significant and were corrected for secular trends. The rate of change per day in lead levels averaged -36.6% from trimester 1 to trimester 2, 18.3% from trimester 2 to trimester 3, and -40.8% from trimester 3 to delivery. The patterns in our study were consistent with the patterns reported in a few other longitudinal studies of change in lead level during pregnancy. Findings reveal significant associations between maternal blood lead levels and both hematocrit and trimester of pregnancy. Clinicians who interpret test results should take into account the dynamics of these variables when determining appropriate care for both mother and neonate.