Teratology is the study of birth defects, including their etiology, pathophysiology, and epidemiology. More broadly, teratology is the study of perinatal developmental injury or abnormal development and of the factors including birth accidents and genetic mutations that increase the risk of developmental injury. Thus, the field covers the impact of exposures to exogenous agents or events (called teratogens) during specific developmental phases on physical and functional outcomes. Among such outcomes may be physical malformation, growth abnormalities, disruption in function in one or more organ systems including the central nervous system, and death. Among the agents or events of interest are both prescribed and illicit drugs, industrial chemicals, environmental pollutants, irradiation, viral infections, traumas such as preterm birth, and psychological conditions such as increased perinatal stress ...