[Histologic and biochemical studies of the uteri of ovariectomized gilts during the first two months of pregnancy after different hormone substitutions. 2. Effects of reducing the progesterone dosage on the survival rate of embryos and the structure of the placenta and the influence of oral administration of norgestrel].

Studies were conducted into ovariectomised gilts in early gravidity, with the view to finding out if reduction of daily progesterone doses had an impact upon embryo survival rate and on the structure of the placenta and if experimentally induced progesterone deficit could be offset by oral administration of norgestrel, a synthetic progestagen. Embryo survival were found to drop from 80 to 26.1 percent in response to reduced progesterone dosage from 120 mg to 40 mg, average numbers of living embryos per animal being 9.6 or 3.0. Oral administration of 12 mg of norgestrel, in addition to injection of 40 mg of progesterone, enhanced the survival rate to 64.6 percent, the average number of living embryos coming to 8.9. Reduction of progesterone doses compared to animals with sufficient progesterone supply. Depressed the beginning decrease of the thickness endometrium and surface epithelium oedematisation of the endometrial stroma was mitigated, and subepithelial hyperaemia disappeared altogether. The secretory activity of uterine glands declined, and so did the endometrial activities of acid and alkaline phosphatases. Administration of norgestrel proved helpful in substantive removal of manifestations observed in the progesterone deficit group.