Low level lead exposure and pregnancy outcomes in an observational birth cohort study: dose–response relationships

Abstract

BackgroundNational and international guidelines on safe levels for blood Pb in pregnancy focus on a threshold above which exposure is of concern. However, it has recently been suggested that the decrease in birth weight per unit increase in blood Pb is actually greater at lower than at higher concentrations of Pb without evidence of a lower threshold of effect. Our aim was to investigate whether there was evidence for a differential effect of maternal Pb levels on birth outcomes and/or a threshold value for effects.MethodsBlood samples from pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) were analysed. Data collected on the infants included anthropometric variables. We fitted adjusted multivariable fractional polynomial models for birth outcomes.ResultsAdjusted models that assumed a linear relationship between untransformed blood Pb and the outcomes provided the best fit: an increase of 1 µg/dl was associated with changes in birth weight of −9.93 (95 % CI −20.27, 0.41) g, head circumference −0.03 (95 % CI −0.06, 0.00) cm and crown–heel length −0.05 (95 % CI −0.10, 0.00) cm.ConclusionThere was no evidence in this study to suggest a supralinear dose–response relationship or a lower threshold for the effect of maternal blood Pb on birth outcomes. This has implications for consideration of national and international guidelines on levels of concern in pregnancy. Exposure to Pb should be kept as low as possible during pregnancy to minimise adverse outcomes.

Effects of intrauterine exposures to polychlorinated biphenyls, methylmercury, and lead on birth weight in Japanese male and female newborns

“…Given the concurrent exposure model of environmental pollutants, the principal findings of our study were that birth weight was associated with ΣPCB concentrations in the male and female newborns, and also with THg concentrations in the male ones. However, the significant relation to lead was not seen, probably not only because of low lead levels but also the extremely narrow range of lead exposure, as compared to the values reported previously [ 2 – 6 ]; whereas, Taylor and coworkers could not find any evidence suggesting a dose–response relationship either in 4190 births (median of maternal blood lead, 3.40 μg/dL; range, 0.20 - 19.14 μg/dL) [ 40 ]. In addition, no evidence of multicollinearity problem among ΣPCB, THg, and fish/seafood intake or of interaction between sex and toxic substances on birth weight was suggested, because all the VIFs were less than 2 in the present study [ 39 ].…”

Heavy metals exposure levels and their correlation with different clinical forms of fetal growth restriction

“…Nevertheless, the influence of heavy metals on neonatal birth weight has been disputed in the literature. Recent data have also suggest that there is no change in birth weight from heavy metals exposure [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”

Relation between low birth weight and Maternal blood lead levels in Sidi Bel Abbes, Algeria: a case-control study

“…Other Study sought to evaluate the relationship between toxic metals, nutrient combinations and birthweight among 275 mother-child pairs found that prenatal blood Pb was associated with lower Birthweight. Essentials elements Fe, Se, Ca and folate did not modify these relations [18].Taylor et al, examinedBlood samples of pregnant women derived from theAvon Longitudinal Study of Parents and Children (ALSPAC) and suggest that an increase of 1 μg/dl was associated with changes in birth weight of −9.93 g, head circumference −0.03 cm and crownheel length −0.05 cm [19].…”