Pregnancy outcome confounders

Thus, because of the wide range of PbB levels, the apparent lack of confounding by social class and the large number of women involved, this prospective study promises to answer many issues surrounding the possible influence of lead exposure on pregnancy outcome. It is still too early, however, for us to present any definitive data concerning pregnancy outcome. 

TTP information. As with other NYS Angler Cohort studies, limitations include the reliance on self-reported exposure data and outcome data, and the lack of information on potential confounding factors such as occupational exposures, alcohol and caffeine consumption, and current smoking status. In addition, women with unplanned pregnancies were necessarily ruled out from the analysis Buck et al. (1997) noted that this may be a potential bias inherent in the study. 

No studies have demonstrated that selenium or its compounds are teratogenic in humans. Robertson (1970) reported on the outcome of pregnancies in a laboratory in which workers handled sodium selenite. Of the five pregnancies, four ended in spontaneous abortion and one resulted in an infant with bilateral clubfoot. The urinary selenium levels in all subjects were similar to those in other individuals living in the same area. The limited number of cases, possible exposure to other toxic agents, and other confounding factors leave the relationship between sodium selenite and developmental effects inconclusive. 

The ability of a xenobiotic to bind reversibly to a receptor does not preclude its being bioactivated to a reactive intermediate, or vice versa (Fig. 5). Similarly, for some birth defects, both mechanisms potentially could contribute to the same teratological outcome, and different mechanisms may predominate in different strains and species at different gestational times of pregnancy, or in different embryonic-fetal target tissues or cell t3 pes. These possibilities often confound a precise elucidation of the mechanism of teratogenesis for a given xenobiotic. 

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