Effects of a gonadotropin-releasing hormone antagonist on hormonal levels in the pregnant baboon and on fetal outcome

In order to study the function of a gonadotropin-releasing hormone (GnRH) in pregnancy, a GnRH antagonist was administered to pregnant baboons (35 to 45days’ gestation) over 7days. A marked suppression of progesterone, estrone, and estradiol was observed during treatment. In two animals, estrogens were still suppressed later in pregnancy (days 95 to 116), and delivery resulted in stillbirths. In one of these animals the placenta was recovered, and it was half normal size. In the third animal, the circulating steroids, including the estrogens, returned to normal levels following antagonist administration, and a small live-born fetus was delivered. These data indicate that interference with GnRH activity during early pregnancy can result in stillbirths, possibly due to induction of placental insufficiency. Thus, these studies support the hypothesis that chorionic GnRH has a physiologic function during pregnancy in the control of placental hormonogenesis and normal fetal outcome.