The possible role of prostaglandins in the hyperfunction of the renin-angiotensin-aldosterone system in the newborn.

Plasma renin activity and plasma aldosterone concentration were measured by radioimmunoassay in eight newborn infants born vaginally to mothers on indomethacin treatment. Measurements were made in venous cord blood at birth and on the sixth day of life. The results were compared to those obtained in eight healthy control newborn infants of similar gestational age and birth weight. Maternal treatment with indomethacin was associated with a decrease of plasma renin activity (mean +/- SD) from 16.71 +/- 2.76 ng/ml/hour in the control group to 9.60 +/- 3.84 ng/ml/hour in the treated group. Plasma aldosterone concentration was lower in the cord blood of the treated group and a similar trend was demonstrated in the sixth day samples. It is suggested that the increased endogenous prostaglandin production during labour may be one of the factors responsible for the development of hyperactivity of renin-angiotensin-aldosterone system in the newborn.