Progesterone and the Accomplishment of Parturition in the Sheep

Abstract

Summary. A flock of thirty ewes was observed through two pregnancies to determine whether parturition could be delayed by the systemic administration of gestagens. In the first season, the four treated groups received daily injections of 2-5 and 10 mg, 6a-methyl-17a-hydroxyprogesterone acetate (6-map) and 10 and 40 mg progesterone for 14 days starting 1 week before the expected date of delivery. The time and course of delivery appeared to be unaffected. The following season the dose levels were increased to 25 and 40 mg 6-map, and 80 and 160 mg progesterone. A high proportion of pregnancies was affected by this treatment. Some sheep delivered to schedule but most of the others had to be subjected to Caesarian section. The mortality of lambs delivered at term was higher than in the control group and in all the cases of delayed parturition the lambs died in utero. The foetal death was not considered to be due to post-maturity. The results are discussed and it is concluded tentatively that placental progesterone in the ewe is not replaceable by systemic progesterone.

Induction of premature delivery in sheep following infusion of cortisol to the fetus. I. The effect of maternal administration of progestagens

“…unless supraphysiological doses of progesterone were administered. Although administration of progesterone has also been shown $49 delay or prevent prematurely induced or normal parturition in cattle and swine as well as in sheep (Bengtsson and Schofield 1963;Nellor 1963; J6chle ~t a / . 1972; Fairclough et al %984), an increased incidence of distocia and fetal death whs reported.…”

“…In the sheep, administration of progesterone during late pregnancy, when given in physiological doses of 80 mg/day for a week at around the time of parturition (Bengtsson and Schofield 1963) or BOO mg for 4 days during a fetal infusion of dexamethazone QLiggins et ad. 1972), failed to delay noma% or dexarnethazone-induced parturition.…”

“…1977). When this decrease in progesterone production was countered by exogenous progesterone (up to 108 nag/% h) myornetrial progesterone concentration was maintained but delivery still occurred and it was not until 200 mg progesterone/24 h was administered to sheep that normal or induced parturition could be inhibited (Bengtsson and Schofield 1963;kiggins el al. B 972).…”

Fetal Rat Adrenal Gland Steroidogenesis in vitro in Prolonged Pregnancy

“…In normal pregnancy the placenta transports nutrients from the mother to the fetus and synthesizes a high amount of progesterone which regulates pregnancy (10,11). The weight of fetal rat adrenal glands, plasma corticoste rone level and adrenal corticosteroid synthesis in vitro from 4-14C-progesterone increased from the 17th to the 21st day of pregnancy and quickly decreased on the 22nd day of preg nancy (1)(2)(3)(4)(5).…”

Physio-pathologic studies in induced parturition in the cow (Bos taurus)

“…Exogenous progesterone did not delay the onset of labor in the ewe (Bengtsson and Schofield, 1963;Liggins e;t aJ^. , 1972) but it sometimes caused a protracted delivery.…”