Deformation

A change from the normal size or shape of a structure produced by mechanical forces that distort an otherwise normal structure. Deformations occur most often late in pregnancy or during delivery. A twin pregancy can cause deformations due to crowding of the twins late in pregnancy. A well-known example of a deformation is molding of the head of a baby born by vaginal delivery. There are usually no significant lasting effects of a deformation. A deformation is different from a malformation in timing and impact. In a malformation, the development of a structure is arrested, delayed, or misdirected early in embryonic life and the effect is permanent.

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1. Deviation of form from the normal; specifically, an alteration in shape and/or structure of a previously normally formed part. It occurs after organogenesis and often involves the musculoskeletal system ( e.g., clubfoot). 2. In rheology, the change in the physical shape of a mass by applied stress. [L. de-formo, pp. -atus, to deform, fr. forma, form]

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de·for·ma·tion (de″for-maґshən) [L. deformatio a disfiguring] 1. in dysmorphology, a type of structural defect characterized by the abnormal form or position of a body part, caused by a nondisruptive mechanical force. 2. the process of adapting in shape or form, as the change in shape of erythrocytes as they pass through capillaries.