[Sequential study of the plasmatic atrial natriuretic factor and the urinary excretion of an ouabain displacing factor and of dopamine in normotensive pregnant women before and after labor].

Estimation of urinary excretion of a ouabain displacing factor (ODF) and dopamine was carried out immediately before delivery, 7 days and 70-90 days after delivery in 12 normotensive pregnant women. Simultaneous estimation of plasma 99-126 atrial natriuretic factor (ANF), plasma renin activity (PRA) and plasma aldosterone were also undertaken. The data were compared with those obtained in a non pregnant normotensive group of women (n = 14) and a group of pregnant normotensive women in the early third trimester (n = 14). Urinary ODF and dopamine were significantly higher in the early third trimester when compared with non pregnant women but immediately before delivery, ODF excretion had fallen below non pregnant values and dopamine excretion had dropped to control values. Both remained low after delivery. Plasma ANF was higher in pregnant women when compared with non pregnant controls and remained high just before delivery and 7 and 70-90 days after delivery. PRA and plasma aldosterone were higher during pregnancy and had fallen to non pregnant values 7 days post-partum. It is concluded that there is considerable discrepancy in the evolution of natriuretic and antinatriuretic factors before and after delivery and that the drop of PRA and aldosterone by 7 days post-partum, contrasting with the unchanged high values of ANF, may contribute to negative sodium balance after delivery.