ABSTRACT
This chapter discusses three different environmental influences on prenatal development: alcohol, cocaine, and exercise. Alcohol readily crosses the placenta and enters the fetus’ bloodstream. Alcohol is metabolized and eliminated much more slowly in the fetus and in the newborn than in the mother. Recreational drugs such as heroin, methadone, cocaine, crack, and marijuana have been noted to have deleterious effects on the fetus and newborn when used by the mother during pregnancy. The exercise of pregnant women must be closely monitored because of the dramatic physiological changes induced by pregnancy. The immediate effect of exercise is that blood is diverted from the uterus to the legs. Drinking alcohol, using cocaine, and engaging in exercise programs are not isolated events randomly distributed across the population. Contradictions between animal and human studies may be due to the voluntary nature of exercise in humans, which may be less stressful than forced exercise or other stressors used in animal studies.
