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  • Title: [Induction of abortion by oestrogens in animals. A review (author's transl)].
    Author: Velle W.
    Journal: Nord Vet Med; 1974 Oct; 26(10):563-71. PubMed ID: 4616221.
    Abstract:
    The mechanism by which estrogens induce contraception and abortion in mammals is detailed. The transportation of the ovum in the Fallopian tubes, the length of the period from conception to implantation, and the type of placenta are the variables that determine the effectiveness of inducing contraception or abortion with estrogens. In animals with plac enta hemochorialis and eccentric or interstitial implantation, estrogens have a contraceptive effect. In rats, the transportation of the ova to the uterus takes a relatively short time, so estrogens in dosages of 20 mcg counteract the progesterone produced by the corpora lutea, speeding up the ovum's entry into the uterus before it is prepared to receive the ovum. In larger dosages estrogen constricts the tubes at the isthmus, preventing the ovum from reaching the uterus. Enucleation of the corpora lutea in rabbits results in a decrease of progesterone and a corresponding increase in estrogen in the uterus, causing fertilized ova to be transported out of the uterus itself more quickly. Subcutaneous injections of estradiol and estrone in varying dosages will cause contraception in rats, mice, and rabbits. In apes, diethylstilbestrol taken orally causes contraception. These animals all have placenta hemochorialis. In animals having placenta epitheliochorialis, central implantation, and low endogenous estrogen production, like sheep, horses, and ruminants, estrogens can be used to produce abortion. The estrogens loosen the placenta from the uterus, cause the loss of the decidua and vacuolization of the endometrium, which results in the death of the fetus. This use of estrogens to produce abortion has also been observed in animals with placenta hemochorialis, but greater dosages are required than to produce the contraceptive effect. Inducing abortions with estrogens had no effect on future fertility in the laboratory specimens.
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