Plasma renin activity in maternal and umbilical cord blood during parturition.

Plasma renin activity (PRA) in umbilical cord blood exceeded that of maternal blood in 14 out of 20 cases. Fetal PRA was not significantly correlated to maternal PRA. Significantly higher fetal renin values than the corresponding maternal ones were restricted to shorter labor (N equals 10). In cases with uterine inertia (N equals 8) higher values than in normals (N equals 7) were observed, whereas suppressed maternal and cord blood levels were found in maternal fluid retention with edema (N equals 3). The data suggest that fetal production of renin may be largely independent of maternal renin secretion.