Phenomenon of Teratogen

On the face of things, the generally accepted definition of a teratogen would appear to be straightforwardly informative. Mosby's initially defines a teratogen as "any substance, agent, or process that interferes with normal prenatal development, causing the formation of one or more developmental abnormalities in the fetus" (Teratogen, 1998, p. 89). However, amplification of the definition demonstrates the complex functionality of teratogens: What a teratogen is cannot be definitively stated. How it will strike cannot be predicted absolutely, though embryos appear to be most vulnerable between weeks three through twelve of gestation, "when differentiation of the major organs and systems occurs" (p. 89).

The literature contains specific recommendations against use of certain otherwise beneficial pharmaceuticals based on their teratogenic effects on pregnancy outcomes. But repeatedly in studies that form the basis of such recommendations, problems with methodology emerge because of the difficu

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before pregnancy onset poses developmental problems for the fetus. Meanwhile, the absence of some nutrients appears to have a teratogenic effect. Neggers and Others (1997), for example, cite studies showing that zinc deficiency is highly teratogenic in rat subjects, and in their study they compared zinc-level increases in pregnant women whose diets were or were not supplemented by dietary zinc. But they note that controversy surrounds the issue of whether dietary zinc supplements for pregnant women can exercise beneficial effect, since the level of zinc in red blood cells rises anyway over the course of a pregnancy. To put it another way, the study could not prove the absence of dietary zinc supplements to be teratogenic, even though it could show an apparent effect of zinc supplementation on pregnant women. The authors of the Sri Lanka study cite the phenomenon of positive recall bias, the name given to the fact that women giving birth to babies with major congenital defects are likely to report exposure to possible teratogens (De Silva & Others, 1999). This does not mean that clinicians are not alert to the possibility of interference from some unidentified external source with the normal human gestation process. However, rese
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Approximate Pages = 12 (250 words per page)

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