The Port Pirie cohort study: maternal blood lead and pregnancy outcome

During a three-year period, 831 pregnant women in and around Port Pirie, South Australia--a lead smelter community with longstanding lead pollution--were enrolled in a cohort study to examine prospectively the relation between body lead burden and pregnancy outcome. Three-quarters of the enrolled women were residents of the Port Pirie municipality; the other women lived in adjacent towns and countryside. At 14-20 weeks' gestation, the Port Pirie resident women had a mean blood lead concentration of 10.6 micrograms/dl, while the mean in the other (non-Port Pirie) women was 7.6 micrograms/dl. Similar differences were observed in maternal blood samples taken at 30-36 weeks, at delivery, and from the umbilical cord. These blood lead measures, in conjunction with information collected on other risk factors, were then examined in relation to pregnancy outcome. Among 749 pregnancies followed to completion, pre-term delivery was statistically significantly associated, in a dose-response manner, with maternal blood lead concentration at delivery. Mothers of late fetal deaths (stillbirths) had blood lead concentrations at 14-20 weeks' gestation similar to those of all the other women but had lower concentrations at delivery than the other women. Outcomes of pregnancy for which no association with blood lead was detected were spontaneous abortion, low birthweight (for births at term), intrauterine growth retardation, premature rupture of the membranes, and congenital anomalies.