Umbilical-cord plasma progesterone in term infants delivered by caesarean section.

Plasma progesterone concentration was measured by radioimmunoassay in blood samples taken from 67 patients delivered by lower-segment caesarean section (LSCS). Blood samples were taken from umbilical-cord artery and vein and from a peripheral maternal vein. Cord venous progesterone levels were higher (c400 ng/ml) in those patients where the fetus was clinically in jeopardy and this was the principal indication for section. Patients in whom the fetus was not in jeopardy had lower cord venous progesterone concentrations (c300 ng/ml) regardless of whether or not they were in labour. Maternal levels of progesterone were similar in all patients. The advantage to the fetus of these varying progesterone concentrations is not clear, but the evidence lends support to the hypothesis that the fetus exercises control over placental progesterone production during parturition.