Prenatal Exposures

Although exposures of the ovum or the sperm prior to conception may have profound health effects on a child, including development of an abnormal fetus,1 in this section we focus on prenatal influences. In most cases, exposures of the fetus are from maternal exposure. Exposures of the mother during pregnancy can come from many sources; common sources include maternal occupation, substance use, diet and water consumption, and paraoccupation (occupational chemicals or other hazards brought home by other family members). The strongest workplace exposure associations are lead, mercury, organic solvents, ethylene oxide, and ionizing radiation and poor reproductive outcome, including birth defects (Agency for Toxic Substance and Disease Registry, 1993; Schardein, 2000).

Use of tobacco, alcohol, and illicit drugs also have harmful effects. Tobacco use during pregnancy is a major cause of fetal and newborn morbidity and mortality (small for gestational age, persistent pulmonary hypertension, sudden infant death syndrome, poorer intellectual functioning) (Nicholl, 1989; Golding, 1997; Day et al., 1992; Kline, 1987; U.S. Environmental Protection Agency, 1992; Bearer et al., 1997). Heavy drinking during pregnancy is the cause of fetal alcohol syndrome (FAS), the leading known cause of mental retardation (Abel and Sokol, 1987; Sokol, Delaney-Black, and Nordstrom, 2003). Conservative estimates place the incidence of FAS at 0.33/1,000 live births (Abel and Sokol, 1991). More common effects include alcohol-related birth defects, alcohol-related neurodevelopmental defects, and subtle effects on a variety of behavioral, educational, and psychological tests resulting from low to moderate levels of drinking during pregnancy (Institute of Medicine, 1996). While the effects of maternal prenatal use of cocaine, opiates, and methamphetamines on infant cognitive development and behavior remain controversial (owing to confounding environmental factors) (Bays, 1990; Tronick and Beeghly, 1999), the effects on maternal-infant interactions are more established (Breiter et al., 1997; Singer, 2000).

There are multiple short critical periods during the development of a fetus when a short, acute exposure may cause a problem. For this reason, exposures need to be tracked as highs and lows on a daily basis rather than as monthly averages. For example, water quality is regulated by monthly averages. However, a daily peak may exceed a threshold of concern and still be within the regulatory limit.

A recent review concluded that neural tube defects and small-for-gestational-


For example, prematurity (Herbst, 1980; Kaufman et al., 2000) and hypospadias (a congenital abnormality in which the urethral opening is not at the tip of the penis) (Klip et al., 2002) increased among the grandchildren of pregnant women who took DES (diethylstilbestrol), and sperm exposure resulting from occupational exposures increases the risk of cancer (Feychting et al., 2001; Colt and Blair, 1998) and birth defects (Chia and Shi, 2002) in offspring.

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