Termination of pregnancy in macaques (Macaca radiata) using monkey antiserum to ovine luteinizing hormone

The ability of a monkey antiserum to ovine LH to interrupt gestation in monkeys has been established. The antiserum has been shown to neutralize monkey pituitary LH by a number of criteria. The significant increase in serum progesterone level on day 23 of the cycle shown by mated monkeys has been used as an index of pregnancy. Injection of LH antiserum during the first week of missed menses (day 29–31 of cycle or day 18–20 of gestation) causes significant reduction in serum levels of progesterone followed by onset of bleeding which is interpreted as the termination of gestation. The same dose of non-immune serum given to monkeys during the same period does not have any deleterious effect on the progress of pregnancy. The antiserum-treated animals after the termination of gestation, resume cyclicity. Injection of antiserum after day 25 of gestation does not bring about termination of pregnancy. It is suggested that by using antisera raised in humans to ovine LH, this method may be developed as a fertility control measure in humans.