Alveolar carbon dioxide tension levels during pregnancy and early puerperium.

Abstract

THE persistence of an elevation of the basal body temperature during the early months of pregnancy is a classic example of the continuation of a systemic response, which, in the nonpregnant state, is characterized by a cyclic ebb and flow of temperature changes during the menstrual cycle. The typical hyperthermia, which becomes apparent at about midcycle and which is maintained almost until the time of the next menstruation, is attributed to the action of progesterone (1, 2). In the normally menstruating woman the concentration of carbon dioxide in the alveoli is depressed during the postovulatory phase of the cycle (3–6). The administration of progesterone lowers the alveolar CO2 tension (7–9), and the cyclic fluctuations of this gas are also correlated with those of progesterone production. In the event of pregnancy, as is illustrated in this presentation, the suppression of carbon dioxide tension is continued. Cyclic variations in serum sodium and chloride levels during the normal menstrual cycle have ...