Plasma renin activity in the intervillous space of the human placenta, in umbilical vessels and in maternal peripheral venous blood.

Plasma renin activity (PRA) was measured by bioassay in the maternal and fetal compartments: intervellous space of the placenta (IVS), maternal peripheral venous blood (MPVB), umbilical artery (A) and vein (V), in a group of normal parturients and their respective fetuses, also normal. The material was collected simultaneously from mother and fetus in the third phase of delivery. PRA valuses in the IVS of the placenta were higher than those observed in the umbilical vein, and similar to those found in the MPVB. PRA values in the umbilical cord vessels behaved as if being part of only one compartment. The mechanisms of regulation of plasma renin activity on the maternal side seem to be independent from those on the fetal side, at least under physiological condition.