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Abstract
The total incidence of congenital defects, as reported by various authors, varies considerably with figures ranging from 1 to 3% depending on geographic locality and ethnic origin of the population studied. In about one fifth of afflicted cases, evidence exists for a genetic basis and only in a few percent the cause of the congenital defect can be traced to a known environmental factor.
In contrast to other defects, congenital hearing impairment is often attributable to exogenous agents affecting the fetus during pregnancy. Nevertheless, in congenitally deaf children, the unknown etiological group remains the largest and here the most important object for future research is to recognize hitherto unknown exogenous agents, with the ultimate aim of preventing such causes of deafness.
A brief survey is given on the present state of knowledge on the harmful effects of drugs and infections on the fetus's hearing organ, supplemented with some personal observations.
La fréquence des malformations congénitales varie considérablement d'un auteur à l'autre, des chiffres allant de 1 à 3%, selon la localisation géographique et l'origine ethnique de la population étudiée ont été avancés. Dans 1 cas sur 5, il existe un indice d'une cause génétique, tandis que dans un pourcentage réduit de cas, l'origine de la malformation congénitale peut ětre trouvée dans un facteur environnemental connu.
Contrairement aux autres malformations, les malformations auditives congénitales peuvent ětre attribuées, dans une large mesure à des agents exogènes connus affectant le fœtus au cours de la grossesse; cependant, une taˇche importante de la recherche future sera d'identifier les agents exogènes actuellement encore inconnus.
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