Umbilical cord blood lead

Shucard JL, Shucard DW, Patterson R, et al. 1988. Prenatal lead exposure and its potential significance for developmental disabilities A preliminary study of umbilical cord blood lead levels. Neurotoxicology 9 317-326. 

Although the results are not entirely consistent among studies, the evidence on maternal or umbilical cord blood lead (under 10 gg/dL) and the large number of studies led the NTP to conclude that there was sufficient evidence of an association between maternal BLL under 10 gg/dL and reduced fetal growth and low birth weight. In contrast, the NTP concluded that there was only limited evidence that maternal BLL under 10 gg/dL is associated with spontaneous abortion and preterm birth. Although a number of prospective and cross-sectional studies have reported an association between prenatal BLL under 10 gg/dL and preterm birth, the conclusion of limited evidence was based primarily on inconsistency of the data and a large study of mother-infant pairs that failed to find the same relationship. EPA (2012) also concluded that there was little evidence to support an association between maternal or paternal lead exposure and the incidence of spontaneous abortion. 

Maternal blood lead levels and umbilical cord blood lead levels are the most direct measure of fetal exposure to lead, reflecting recent lead exposure and lead mobilized from tissue stores (Mushak 1989). Recent studies of mobilized... 

Rabinowitz, M., Needleman, H. L., Petrol Sales and Umbilical Cord Blood Lead Levels in Boston, Massachusetts, Lancet 19831 63. 

To assess the association between prenatal/early postnatal lead exposure and development, we followed a group of urban US infants from birth to 2 years of age. Estimates of the association between lead and Bayley Mental Development Index (MDI) scores at ages 6, 12, 18, and 24 months were obtained using several regression options. In all multivariate models examined, MDI scores were associated with umbilical cord blood lead levels, but not with postnatal blood lead levels. Infants with high cord blood lead levels (10-25 jUg/dl) consistently scored 4 to 8 points lower than infants with low cord blood lead levels (< 3 jUg/dl). Infants vulnerability to lead s developmental toxicity appears to be greatest during the fetal period. 

Figure 2 Mean mental development index (MDI) scores at four ages for infants in the three umbilical cord blood lead categories. Scores are least-squares means, derived from a regression equation that included the 12 priori confounders and the cord blood lead category (represented by two indicator variables). Error bars represent one standard error...

The inverse association in this sample between MDI scores and umbilical cord blood lead levels in the 0 to 25 jUg/dl range appears to be robust. Estimates of its magnitude and precision are relatively independent of analytic approach. Furthermore, the association does not appear to be attributable to the inordinate influence of outliers. Most infants with high lead levels contribute to the overall poorer performance of this group relative to infants with lower levels of prenatal exposure. 

Figure 3 Frequency distribution of umbilical cord blood lead concentrations...

Of the several ways we used the blood lead data, only one achieved statistical significance umbilical cord blood lead levels. That measure was highly statistically significant. For these children the subsequent measurements, including protoporphyrin, provided little predictive power. 

Transplacental transfer of lead in humans has been demonstrated in a number of studies, and lead has been identified in umbilical cord blood. In the work of Bellinger et al. (1987a), the mean lead concentration in umbilical cord blood from a sample size of 11,000 women was 6.6 3.2 pg/dL. In a study of 236 pregnant women in Glasgow, Scotland, the geometric mean PbB levels were 14 pg/dL for... 

Lead concentrations in maternal and umbilical cord blood have been reported by Greek researchers for 50 parturient women at delivery. Twenty-five of the women lived in industrial areas with high air pollution, and twenty-five lived in agricultural areas with low air pollution. The mean lead concentrations (expressed as mean standard deviation) for the women living in areas with high air pollution were 37.2 4.7 pg/L in maternal blood and 20 3.4 pg/L in umbilical cord blood (correlation coefficient, r = 0.57). The mean lead concentrations for the women living in areas with low air pollution were 20.5 5.6 pg/L in maternal blood and 12.9 3.6 pg/L in umbilical cord blood (correlation coefficient, r = 0.70). The authors conclude that the placenta demonstrates a dynamic protective function that is amplified when maternal PbB levels are raised (Vasilios et al. 1997). 

Concentrations of lead in umbilical cord blood of two groups of women giving birth in a Boston Hospital in 1980 and 1990 have also been reported. Mean lead concentration of umbilical cord blood was 6.56 3.19 pg/dL forthe 1980 group and 1.19 1.32 pg/dL forthe 1990 group (Hu etal. 1996). 

Lauwerys R, Buchet J-P, Roels HA, et al. 1978. Placental transfer of lead, mercury, cadmium, and carbon monoxide in women I. Comparison of the frequency distributions of the biological indices in maternal and umbilical cord blood. Environ Res 15 278-289. 

Schuhmacher M, Hernandez M, Domingo JL, et al. 1996. A longitudinal study of lead mobilization during pregnancy concentration in maternal and umbilical cord blood. Trace Elements and Electrolytes 13 177-181. 

Vasilios D, Theodor S, Konstantinos S, et al. 1997. Lead concentrations in maternal and umbilical cord blood in areas with high and low air pollution. Clin Exp Obstet Gynecol 24(4) 187-9. 

In any case, it s estimated that the human fetus is ten to a hundred times more sensitive to ambient lead than children or adults, such that the so-called national averages are almost certainly dangerous for the fetus. In 2006, researchers reported a study of 146 pregnant women in Mexico City.13 It s one of the few studies to measure maternal lead values during each trimester of pregnancy. The researchers examined the impact of prenatal lead exposure on fetal neurodevelopment by measuring whole blood and plasma levels of lead in the pregnant mothers at each trimester and then in umbilical cord blood at delivery. When the infants were at 12 and 24 months of age, the researchers measured their BLL and also evaluated their neural development with a standard method (the Spanish version of the Bayley Scales of Infant Development). From the evidence,... 

The concentrations of cadmium in blood of the 51 healthy Austrian mothers was 0.44 (SD 0.4) p.g/1 and in umbilical cord blood 0.08 (SD 0.16) p.g/1. Urine excretion of cadmium (and lead) assayed was normal. The concentrations of cadmium in human milk was below limits of detection of AAS (Plockinger et al., 1993). 

It is well documented that lead crosses the placental barrier (Carpenter, 1974, Lauwerys et al., 1978) and umbilical cord blood has been shown to contain lead in concentrations similar to those found in maternal blood (Harris and Holley, 1972). Although the abortifacient capacity of lead may be due to a direct effect on the fetus, pathological effects on the placenta may also play a role. Baker (1960) showed placental necrosis and haemorrhage, and Dawson et al. (1969) showed that lead may severely depress oxidative metabolism in the toxaemic placenta. 

Chuang, H.-Y., Schwartz, J., Gonzales-Cossio, T., Lugo, M.C., Palazuelos, E., et al., 2001. Interrelations of lead levels in bone, venous blood, and umbilical cord blood with exogenous lead exposure through maternal plasma lead in peripartum women. Environ. Health... 

Kelman BJ, Walter BK (1980) Transplacental movements of inorganic lead from mother to fetus. Proc Soc Exp Biol Med 163 278-282 Khera AK, Wibberley DG, Dathan JG (1980) Placental and stillbirth tissue lead concentrations in occupationally exposed women. Br J Ind Med 37 394-396 Korpela H, Loueniva R, Yrjanheikki E, Kauppila A (1986) Lead and cadmium concentrations in maternal and umbilical cord blood, amniotic fluid, placenta, and amniotic membranes. Am J Obstet Gynecol 155 1086-1089 Kuhnert BR, Kuhnert PM, Zarlingo TJ (1988) Associations between placental cadmium and zinc and age and parity in pregnant women who smoke. Obstet Gynecol 71 67-70... 

Rabinowitz MB, Needleman HL (1982) Temporal trends in the lead concentrations of umbilical cord blood. Science 216 1429-1431 Rossouw J, Offermeier J, Van Rooyen JM (1987) Apparent central neurotransmitter receptor changes induced by low-level lead exposure during different developmental phases in the rat. Toxicol Appl Pharmacol 91 132-139 Samarawickrama GP, Webb M (1979) Acute effects of cadmium on the pregnant rat and embryo-fetal development. Environ Health Perspect 28 245-249 Scharpf LG Jr, Hill ID, Wright PL, Plank JB, Keplinger ML, Calandra JC (1972) Effect of sodium nitrilotriacetate on toxicity, and tissue distribution of cadmium. Nature 239 231-234... 

See Elwood, St. Leger, and Morton (1976) and Lauwerys et al. (1977). See also Needleman et al. (1984), who fail to find any correlation between water lead and lead in umbilical cord blood. 

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