Effect of fetal hypophysectomy on the initiation of parturition in the goat.

Fetal hypophysectomy performed between 97 and 130 days of gestation caused a significant (P is less than 0.005) prolongation of pregnancy in 5 goats in which every fetus was treated. Three of these goats gave birth spontaneously. Sham surgery or hypophysectomy of one fetus of twins had no effect on gestation length. Hypophysectomized kids, delivered after prolonged pregnancy, were significantly heavier than normal term kids (P is less than 0.005) and had lighter adrenals (P is less than 0.025). Measurements of maternal peripheral plasma concentrations of progesterone and total unconjugated oestrogens showed that the changes in goats carrying hypophysectomized fetuses were similar to those of normal pregnancy except that the prepartum oestrogen peak was absent, whether or not parturition occurred spontaneously.