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January 12, 1963

Congenital Malformation in Strain A MiceIts Experimental Production by Thalidomide

JAMA. 1963;183(2):139-141. doi:10.1001/jama.1963.63700020034021b

PHOCOMELIA, a congenital malformation that involves nondevelopment of the long bones of one or more of the extremities, occurs only rarely. Recently, Kosenow and Pfeiffer1 and Wiedemann2 reported an increased incidence of phocomelia in the human newborn after use of the sedative thalidomide during early pregnancy. The congenital defects observed under these conditions have been of the most severe types, frequently involving all extremities. Even when the extremities are relatively normal, the prehensile grasp may be lost.3

Difficulties have been encountered in producing such defects with thalidomide in laboratory animals. Studies with thalidomide in rats caused no malformations,4-6 although other studies indicate that the substance passes through the placenta in rabbits.7 According to two reports,6,8 it produces in rabbits abnormalities which are similar to those found in human infants. Recently, abnormalities consisting of harelip, cleft palate, cataracts, and tail deformities have been found as