Effects of vaginal delivery and caesarian section on plasma renin activity and angiotensin II levels in human umbilical cord blood.

High levels of angiotensin II were found in umbilical venous blood of babies delivered vaginally (40.3 pg-ml-1) and vaginally with epidural anaesthesia (66.8 pg-ml-1); low levels of angiotensin II were found in umbilical venous blood of babies delivered by Caesarian section (7.5 pg-ml-1) and in the peripheral blood of normal adults (7.92 pg-ml-1). There were no significant differences between these groups in the levels of plasma renin activity (PRA), although the mean values of PRA showed trends similar to those described for angiotensin II. It is suggested that the increase in PRA may account, in part, for the high levels in angiotensin II seen following vaginal delivery, but additional factors may also be involved.