Progesterone Concentrations in the Peripheral Plasma of Pregnant Ewes Following Infection with an Abortifacient Organism

Abstract

Intravenous inoculation of ewes during mid and late pregnancy with cultures of Actinobacillus seminis resulted iu abortion and premature birth, associated with necrotic lesions of the placenta. Peripheral plasma progesterone concentration declined significantly within 24 h of inoculation; after 3 days, however, it increased temporarily to almost normal levels in those ewes that did not abort within 14 days of inoculation. These changes are considered to reflect diminished placental synthesis of progesterone as a result of placentitis, and plasma progesterone concentration during the later stages of pregnancy may be useful for monitoring immediate placental response in ewes inoculated with abortifacient organisms.