Studies of the Circulatory Adaptation Immediately after Birth

The most urgent problem the newborn infant has to face is the initiation of breathing and the subsequent respiratory and hemodynamic adaptation to extrauterine life. The literature on this subject during the last years has been abundant; for recent general reviews see Cook e t al. (3). Karlberg (14), James (l?), Stern & Lind (18). Nevertheless knowledge regarding circulatory adaptive changes in connection with the initiation of breathing is limited and for the most part has been extrapolated from studies of the status of the circulation before, as well as after, delivery (6, 14), and from studies in animals (6). Respiratory studies have demonstrated that the transformation of the fetal lungs to an organ which functions adequately for respiratory gas exchange proceeds very rapidly indeed; it is principally achieved during the first few breaths (8, 14). For this reason i t is necessary to register and interpret the circulatory dynamics during this transformation arid to correlate them with studies of the respiratory adaptation. The present communication reports observations on the blood pressure recorded in t,he umbilical vessels in the newborn infant immediately post partum and during the first minutes of extrauterine