Classification and aetiology of birth defects

Birth defects are encountered frequently by paediatricians and are important causes of childhood morbidity and mortality. Paediatricians may be called upon to see children with single- or multiple-system birth defects. Birth defects can be classified based on their severity, pathogenetic mechanism or whether they involve a single system or multiple systems. This article reviews the classification of birth defects and gives a flavour of our current understanding of the aetiology of the complex developmental processes involved in the formation of these anomalies.