The rubella story also illustrates a triumph in prevention. As better methods of diagnosing rubella became available in the 1960s (Forbes, 1969), there was more certainty about which rashes and nonspecific symptoms in early pregnancy were due to rubella and which were not. Today, public health policy requiring universal immunization against rubella has virtually eliminated the problem of the congenital rubella syndrome in the United States.

Developmental Neurotoxins

Substances such as drugs and chemicals that are damaging to the developing nervous system are known as developmental neurotoxins. Table 8-1 indicates a number of these agents. Their effects on brain and behavior have been summarized in several comprehensive volumes (Kimmel et al., 1990; Slikker and Chang, 1998), as well as in thousands of original research reports. We use prenatal alcohol exposure as an example of this class of early biological insult. The effects of prenatal alcohol have been studied extensively, and the current state of knowledge was recently considered in depth in an Institute of Medicine report (Institute of Medicine, 1996). Major points related to questions of early brain and behavior development are highlighted here.

The adverse effects of prenatal alcohol exposure are now so widely known and accepted that it is hard to believe that the first report was issued only 30 years ago. Fetal alcohol syndrome was first described in the English-language medical literature in 1973 (Jones and Smith, 1973). Maternal alcohol consumption during pregnancy can lead to facial deformities, loss of neurons, severe neurobehavioral impairment, and impaired cognitive functioning, among other problems. Its consequences appear to persist throughout life (Connor and Streissguth, 1996; Institute of Medicine, 1996; Jacobson et al., 1993; Sampson et al., 1994; Streissguth et al., 1996a). They are not, however, inevitable. One of the perplexing aspects of fetal alcohol exposure is that, even with high doses of alcohol, not all fetuses develop symptoms of fetal alcohol syndrome or alcohol-related neurodevelopmental disorder (see below). Its importance lies in its prevalence and preventability, not its inevitability. Nonetheless, this is a very common cause of harm to the fetus that can be prevented.

Survey data collected by the Centers for Disease Control and Prevention show that the incidence of drinking at levels sufficient to put the fetus at risk for neurobehavioral impairment was 3.5 percent in 1995 (the most recent year for which data are available), with binge drinking the predominant pattern (87 percent of the cases) (Ebrahim et al., 1998). The proportion of women who consume alcohol during pregnancy has decreased since the mid-1980s (Serdula et al., 1991), although much of the decline is due to



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