Abstract
The labor preceding delivery of a depressed neonate with normal acid base status is described. Cardiotocographic (CTG) monitoring was used during the 5.5 hours of active labor. Continuous tissue pH determination was performed during the last 100 minutes of labor. Although the CTG pattern was normal all the time, tissue pH declined to 7.02 one hour before delivery, but reached normal values thereafter. The depression of the neonate could only be explained by the episode of acidosis one hour before delivery.