Congenital Abnormalities

In the past, a great deal of ingenuity was applied to explaining the occurrence of birth defects. In the sixteenth century the French surgeon Ambroise Paré suggested no fewer than 13 possible causes, including the wrath of God, imperfections in "the seed," the imagination of the pregnant mother, and injuries to the uterus during gestation (Paré 1982). The notion that maternal impressions during pregnancy could influence the developing fetus was very persistent. As indicated by Joseph Warkany (1977), a chapter entitled "Maternal Impressions" in J. M. Keating's 1889 Cyclopedia of the Diseases of Children recorded 90 cases of congenital defects, blaming mental trauma suffered by the mother during pregnancy for the abnormalities. Explanations of this sort were advanced in the late nineteenth century because the mechanism of inheritance remained a mystery. Most physicians and biologists, such as Charles Darwin, continued to believe that acquired parental characteristics could be transmitted to offspring under appropriate circumstances. This age-old concept was the basis not only of Jean Baptiste de Lamarck's theory of evolution but also of Darwin's theory of pangenesis (Zirkle 1946; Churchill 1976).

Change came in 1900 with the dramatic rediscov ery of Gregor Mendel's work on the laws of inheritance in peas. In 1902 an English physician, Archibald Garrod, voiced his suspicion that a rare disease in babies called alkaptonuria was hereditary and surmised that this "inborn error of metabolism" (Garrod's term) was due to the lack of a necessary enzyme and that genes (the Mendelian hereditary factors) produced enzymes (Garrod 1908). However, his hypothesis was not taken seriously until it was confirmed in 1941 by George Beadle and E. L. Ta-tum, who had investigated the genetic control of biochemical reactions in a mold — neurospora.

Apart from genetic anomalies, birth defects can be caused by chromosomal abnormalities, by a deleterious environment, or by a multiplicity of factors (Chudley 1985). Definite evidence of environmental action was not adduced until 1941, when N. M. Gregg reviewed 78 cases of congenital cataract, finding a history of maternal rubella infection during pregnancy in all but 10 cases. Twenty years later the "thalidomide scandal" concentrated attention on the teratogenic risk associated with drugs taken during pregnancy. This was followed by the equally dramatic recognition that specific congenital malformations, Kenneth Jones's "fetal alcohol syndrome," could result from maternal alcoholism during pregnancy (Jones and Smith 1973).

Since antiquity, maternal alcoholism had been associated with injury to offspring. But as indicated by Rebecca Warner and Henry Rosett (1975), concern about and research into the potential hazards of maternal alcoholism "virtually disappeared" between about 1920 and 1940. Many reasons can be adduced for this rather sudden change, including the effects of prohibition in the United States and the discrediting of the ancient belief in the inheritance of acquired characteristics. Especially in the nineteenth century, the latter concept was exploited to explain the appearance of many congenital diseases, including damage to an infant born to an inebriate woman. Alcohol was presumed to damage the germ cells, male or female, and hence to have an adverse effect on the offspring. To the nineteenth-century mind, this was an example of the hereditary transmission of disease leading to familial degeneration. By the 1920s such Lamarckian-type hereditary transmission had been largely discredited, and the phenomena it had allegedly explained were now usually ascribed to social and economic disadvantage. Furthermore, the uterine environment was not perceived to be a potential site of teratogenic action until the maternal rubella findings were published in the early 1940s.

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