A single electro-convulsive shock of 45 milliamps. for 0.2 sec. administered through alligator clips attached to the ears in 5 pregnant rats 12 hrs. after mating, had no effect on the course of pregnancy. Of 5 rats shocked once daily for 6 days beginning 12 hrs. after copulation, on the 11th day 2 showed some degranulation of pituitary acidophils, slight reduction in the size of basophils, small or degenerating corpora lutea, and degenerating retarded embryos in the uteri. Of 5 animals similarly shocked for 11 days, all showed these pituitary and ovarian changes, and, in addition, complete destruction of the fetuses with necrosis and sloughing of the decidua into the uterine lumen.