About 2 to 3 percent of all children are born with a birth defect (Van Allen and Hall, 1996). In 2002, there were about 133 million births reported, 90 percent of them in less developed countries (Population Reference Bureau, 2002). Thus in developing countries, about four or more million children are born with birth defects. Birth defects or congenital anomalies are defined as any structural or functional abnormality determined by factors operating largely before conception or during gestation. Birth defects may be apparent immediately after birth or may manifest themselves later in life. As infant mortality and morbidity due to infectious diseases, birth asphyxia, and other causes are controlled, the burden of disease associated with birth defects becomes more important. Comprehensive, reliable data on birth defects are not available for most developing countries. However, there can be no doubt that birth defects cause enormous harm in circumstances where risk factors for many conditions are elevated and resources for health care are limited.
Prevention of certain birth defects can be addressed in almost all settings. This chapter reviews the causes of some of the birth defects that are more prevalent in developing countries and describes ways to reduce their impact through prevention, early identification and treatment, and in settings with more resources, through screening for genetic diseases. A companion report, Reducing the Impact of Birth Defects: Meeting the Challenge in the Developing World (Institute of Medicine, 2003) discusses these topics in greater detail and describes the treatment of birth defects beyond the neonatal period.