■(3) Toxic factors lead, mercury, DDT, radiation, X-ray (4)Immunologic factors Blood type in compatibility between mother and fatus Imcompatibilily due to abo, rh◼ (3)Toxic factors: lead, mercury, DDT, radiation, X-ray ◼ (4)Immunologic factors Blood type in compatibility between mother and fatus. Imcompatibilily due to ABO, Rh