Answer
A birth defect is an abnormal structure or the abnormal position of an organ or structure at birth due to a flaw in prenatal development.
Work Step by Step
There are many causes of birth defects; some of these are drugs( thalidomide, barbiturates, sedatives; alcohol, chemicals, infectious diseases and genetic defects. Congenital abnormalities or genetic defects constitute the the main cause of infant mortality in United States. However, while the causes of some birth defects are identifiable, about 50% are idiopathic -- the causes are unknown.
The study of birth defects is called teratology and many teratogens -- alcohols, smoking, and thalidomide are well known. Sme effects of teratogens include anencephaly ( abnormally small heads), malformed faces, stunted growth, and cardiac and central nervous system defects.
