Classification terms in developmental toxicology: need for harmonisation

Abstract The existence of ambiguities and inconsistencies in the use of terms for structural anomalies is a major problem in developmental toxicology and causes great difficulties for administrative decision makers involved in public health evaluation of chemical substances. The absence of harmonisation of terminology is no longer acceptable for regulatory purposes. The debate is unending, however, refinement and consensus are indispensable. This article is a report of the Second Workshop on Terminology in Developmental Toxicology. Experts from research institutions, regulatory agencies, and industries took part in this workshop, which has started a process of discussion that eventually will lead to a harmonisation of terminology used for classification of structural anomalies. The participants put forward a scheme of classification for foetal abnormalities that consists of only two categories: “malformation and variation.” Finally, consensus was achieved in defining the terms malformation and variation. Malformation is defined as a permanent structural change that is likely to adversely affect the survival or health of the species under investigation. The term variation is defined as a change that occurs within the normal population under investigation and is unlikely to adversely affect survival or health. This change might include a delay in growth or morphogenesis that has otherwise followed a normal pattern of development.