Estimation of progesterone in biological tissues and fluids from pregnant women by double isotope derivative assay

A double isotope derivative method has been used for the estimation of progesterone content of tissues and fluids obtained from pregnant women. Progesterone levels are reported for placenta, fetal membranes, myometrium, amniotic fluid and peripheral plasma collected by cesarean section during late gestation. Analyses of progesterone levels in peripheral plasma collected at intervals during 24 hours near term are reported which show no variations in these levels greater than the error of the method. Analyses of peripheral plasma progesterone levels in pregnant women coincident with the course of hypertonic saline-induced abortion are reported. These show significant decreases in progesterone levels (33%) between the time of injection and the onset of clinical labor and a further drop (11%) between the initiation of labor and delivery. The association of fetal death in utero with a lowering of progesterone in peripheral plasma is made which correlated with the length of fetal demise.