Fetal acid-base balance. I. Interdependence of maternal and fetal PCO2 and bicarbonate concentration.

This paper presents the results of measurements of the acid-base and gaseous status of maternal and fetal capillary blood at the time of amniotomy, before the onset of labor. The correlation coefficient between maternal and fetal bicarbonate concentration is 0.6, and that between maternal and fetal PCO2 is 0.31. From the results obtained, as well as from a survey of other work in the field, it is proposed that the diffusion of carbon dioxide across the placenta could not explain some of the findings and that bicarbonate concentrations equilibrate across the placenta.