Adverse effects on the developing organism, which may be detected at any point in the life span of the organism, may result from exposure, prior to conception, of either parent, during prenatal development, or exposure postnatally up to the time of sexual maturation. Researchers are only beginning to identify those exposures and levels of exposures that affect reproductive outcome. According to Matthew Longnecker, National Institute of Environmental Health Sciences (NIEHS), the environmental risk factors for other reproductive outcomes can differ from those for preterm birth.

The potential risk factors studied can be divided into a number of broad categories, including: occupation or occupational exposures, air pollutants, exposure to POPs (persistent organic pollutants), exposure to DDE (1,1-dichloro-2, 2-bis(chlorophenyl) ethylene) a metabolite of DDT (1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT), and PCBs (polychlorinated biphenyls), metals (e.g., lead, arsenic), water disinfection byproducts, and video display terminals.

FIGURE 4.1 Sheep that ingest the flowering plant Veratrum californicum during pregnancy prolong the length of gestation. A pair of twin sheep delivered at 230 days of gestation by cesarean section (left), approximately 80 days longer than the normal pregnancy (right). This would be equivalent to a woman being pregnant for 15 months and not showing any indication of entering the stages of labor.

SOURCE: Binns et al., 1964. © 1964 Annals of the New York Academy of Sciences. Reprinted with permission.

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