Foetal lead exposure

Dietrich KN, Krafft KM, Bier M, et al. 1989. Neurobehavioral effects of foetal lead exposure The first year of life. In Smith M, Grant LD, Sors A, eds. Lead exposure and child development An international assessment. Lancaster, UK Kluwer Academic Publishers. 

Dietrich, K.N., Krafft, K.M. and Bomschein, R.L. (1987). Low-level foetal lead exposure effect on neurobehavioural development in early infancy. Pediatrics, 80, 721-730. 

Neurobehavioural Effects of Foetal Lead Exposure The First Year of Life... 

No adverse effects of postnatal lead exposure (CumPbB, MaxPbB) on Bayley developmental outcomes were found. However, Table 4 shows that a number of effects were found for the foetal lead exposure variables (PbBPre, PbBl) PbBPre was negatively associated with 12-month PDI. The significant PbBPre-by-race interaction indicates that this effect was most pronounced among white infants. Foetal exposure variables were directly related to two IBR... 

Table 4 Results of multiple regression analyses of the effects of foetal lead exposure on Bayley developmental variables...

The findings of a direct relationship between foetal lead exposure and IBR activity level and social-emotional tone factors may have important implications for later intellectual status. For example, transactional models of development suggest that infant behaviours can affect the level and quality of stimulation and care received from the primary caregivers (Sameroff and Chandler, 1975). Sameroff (1978) found that measures of infant emotional tone were superior to Bayley MDI in predicting later childhood IQ. Structural analyses showed that this relationhip was mediated by the level and quality of maternal stimulation more difficult infants received less adequate care. It may be found that foetal lead exposure indirectly influences later intellectual status through infant behavioural factors which can influence the quality and quantity of caregiving. 

Both measures of foetal lead exposure (PbBPre and PbBl) were associated (directly and indirectly) with small deficits in 12-month behavioural performance. 

While current or longer-term health significance of these effects for all individuals cannot be precisely determined, results of studies of the early neurobehavioural effects of low-level foetal lead exposure should be seriously considered by public health officials when setting standards for human exposure. 

Various investigators have reported an association of low-level lead exposure in the foetal period and neonatal outcome measures. These studies differ, of course, with respect to the populations sampled and other procedural features. What is striking, however, in reviewing these is the lack of consistency between studies in the specific outcome measures related to foetal lead exposure. Several features of the research designs that could account for some... 

First, the possibility will be considered that some unmeasured or undermeasured confounding conditions may be particularly crucial to gestational lead exposure and to neonatal outcome measures. The second possibility to be considered is whether discrepancies between studies with respect to correction of blood lead level (PbB) for haematocrit percent (Hct%) may be related to discrepant results. Data from our Cleveland study will be used to illustrate some of these issues. While this commentary is limited to neonatal outcome measures, the issues raised are also relevant to prospective analyses relating foetal lead exposure to later development. 

Table 1 Neonatal outcome measures related to one or more indicators of foetal lead exposure in one or more studies... 

Neurobehavioural effects of foetal lead exposure the first year of life... 

Evidence from several recent prospective and retrospective studies indicates that lead may be psychoteratogenic at relatively low levels of foetal exposure. In the present interim study, lead measured in whole blood during the prenatal (maternal blood lead) and neonatal periods was found to be inversely related to a complex of sensorimotor developmental indices at 6 and 12 months. Prenatal blood lead was also related to lower birth weight, which in turn was related to poorer sensorimotor performance in infants during the first year. These adverse effects were observed at levels of lead exposure common in pregnant women in the United States, Europe, and other developed areas. 

In an interim study of 185 innercity infants in Cincinnati, Ohio, we previously reported (Dietrich et al, 1986) an Indirect adverse effect of prenatal lead exposure on the 6-month Bayley MDI and Psychomotor Development Index (PDI). The effect was mediated by lead-related deficits in foetal growth (birth weight) and maturation (gestational age by physical examination). These relationships are illustrated by the structural equation model shown in Figure 1. 

Are the developmental deficits associated with prenatal lead exposure still mediated through foetal growth and maturational factors ... 

Fetotoxicity Exposure to lead early in life may be a risk factor for foetal growth. A study measured maternal and cord BLLs and examined their associations with birth outcomes. Mother-infant pairs (n = 252) were selected from a... 

Exposure to Q fever organisms in pregnant women may lead to high rates of foetal infection and the subsequent risk of miscarriage. 

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