Pregnancy disturbances in rats by the administration of large doses of sex hormones.

While adequate amounts of sex hormones are necessary for conception and maintenance of a normal course of pregnancy, many investigators have reported that sex hormones administered in large doses caused two kinds of pregnancy disturbances; the first, preventing conception by suppressing ovulation and interrupting the processes of fertilization, tubal transport and nidation of fertilized ovum(Smith, 1926; Parkes and Bellerby, 1927; Burdick et al., 1940), the second, disturbance in the course of pregnancy by abortion, fetal death(Hugget and Pritchard, 1945; Jost, 1945), fetal intersexuality and prolonged period of pregnancy. Large doses of progesterone which has recently been widely used in gestation occasionally produced female hermaphrodites. However, the correct dosage, term, and period of administration of sex hormones, as well as the mechanism of such pregnancy disturbances, have not yet been fully established. The present study was therefore undertaken to contribute to the elucidation of these questions with particular emphasis on the action of sex hormones in interrupting pregnancy and influencing the fetus, using rats as experimental animals.