IN PREVIOUS reports 1 • 2 estimates were made of the difference in the oxygen pressure of fetal and matemal blood as each passes through the human placenta. Such information not only enables one to assess quantitatively the normal limitation placed by the placenta upon the free movement of oxygen from one circulation to the other but also aids in evaluating the effect of abnormal and postmature pregnancy on oxygen transfer. Although these observations are of obvious importance, the clinician is primarily concerned with such questions as the following: (a) What measures may be taken to improve the position of the fetus when the limitation to oxygen transfer exceeds a normal range 1 (b) What can be done to forestall or mitigate intrauterine hypoxia~ These questions are understandable, for, in modern obstetrics, it is generally accepted that the threat of hypoxia is the greatest danger to which the fetus in utero is exposed; it is the most common cause of intrauterine death. Following up the important observations of Lund, 3 obstetricians have adopted the procedure of giving a patient oxygen when signs of fetal distress a})pear. During the past few years, in the Department of Obstetrics at the .Johns Hopkins Hospital, a large number of normal parturients have received oxygen 10 to 15 minutes before delivery; the administration of prophylactic oxygen to all parturients has been advocated by Eastman. His recommendation was based upon the general feeling that oxygen transfer to the fetus was enhanced, and this belief was based upon an increased oxygen saturation of umbilical vein blood. The interpretation of this latter finding is difficult for two main reasons. First, equally high values of umbilical vein oxygen saturation have been obtained in cases where no oxygen was given. Second, it is generally
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