Congenital Malformations

The complacency with which congenital anomalies were once interpreted as expressions of faulty inheritance was rudely shaken in 1940. A convincing demonstration had just occurred in Australia that German measles contracted early in pregnancy by the mother may initiate congenital cataract , deafness, or congenital heart disease in the fetus. A great area for medical exploration had opened. To appreciate the consequences of the discovery, consider the impact on the then current interpretation of congenital cataract-that its presence or absence was determined by genetic factors. Almost without dissent or even questioning, the clinical entity was presumed by physicians to be an inherited defect. For example, in one textbook of wide repute, the occurrence of a single case of congenital cataract in a family of over 40 members was interpreted as indicating a mutation. At the time the book was prepared no one could challenge the inference as unreasonable, but after 1940 anyone had the right to raise the questions: "How do we know that the mother didn't have rubella during pregnancy?" Or, "How do you know that other intercurrent or metabolic illnesses, accidents or operations acting during pregnancy did not cause the defect?" Since German measles was accurately described as long ago as 1840, it may be profitable to digress just a moment in order to examine why the simple cause and effect relation between maternal infection and congenital defects had not been recognized earlier. The answer, I am sure,. lies in the natural behavior of rubella. Ordinarily it is one of the "common communicable diseases of childhood," and relatively few adults are spared to become component parts of the susceptible population. Only half of these would be married at any one time, and less than half of the susceptible married women would be expected to be pregnant. Even of these, only one third would be in the first trimester of pregnancy. Thus, the chances are small for any one physician to see many cases of rubella during early pregnancy in the course of his professional life. Moreover, only 25 per cent of women with first trimester rubella get into trouble; and the risks that * Professor of Preventive Medicine and Epidemiology.