SYSTEMIC LEVELS OF PLASMA PROGESTERONE DURING PREGNANCY IN WOMEN AND MONKEYS1

Abstract

Bio-assays for free and bound progesterone were performed on peripheral venous blood samples obtained, usually at weekly intervals, throughout most of pregnancy in 2 women and 3 monkeys. Concns. of bound progesterone were invariably less than 0.6 [mu]g./cc. plasma. Levels of free progesterone were relatively low, not exceeding 2 [mu]g./cc. of human plasma and 3 [mu]g./cc. of monkey plasma. Peaks in concn. of the hormone recurred with some regularity. Peripheral blood levels of progesterone just before and at the time of delivery were more often high than low.