deformation

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 and during delivery. For example, a twin pregnancy 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. A deformation is different from a malformation in both timing and impact. See also malformation.