Congenital malformations in nonhuman primates: Spontaneous and experimentally induced

An attempt to survey spontaneous teratogeny among nonhuman primates bred under laboratory conditions revealed interesting but nonconclusive results. Data on controlled breeding in 2950 animals representing 12 species yielded an estimated incidence of 0.44% malformations. No indication was found that other primates display more malformations than man, and the limited information available suggests that there may be fewer spontaneous defects in nonhuman forms. Macaques and baboons appear to respond in a similar manner and to the same types of extrinsic agents as does man. Thalidomide, Rubella virus and androgenic hormones produce similar defects in comparable dosage at equivalent stages in development in both groups. Several other agents thought not to be teratogenic in man have been realistically tested in primates and also found to be non‐teratogenic. Using thalidomide an attempt was made to determine the degree of sensitivity and delimit the susceptible period of Macaca mulatta to this drug. Typical limb malformations were obtained with a single dose of as little as 16 mg/kg between the twenty‐fifth and thirtieth days of gestation. Comparable doses at earlier and later ages were without effect, thus defining the susceptible period. In addition, evidence of a positive dose‐response relation and of a cephalocaudal gradient in teratogenesis was obtained.