Continuous fetal scalp tissue pH monitoring during labor. An analysis of 152 consecutive cases.

Continuous scalp tissue pH monitoring was performed in 152 consecutive cases. The success rate was 53 per cent. The average duration of pH monitoring was 151 minutes (range 0--609 minutes). A good correlation was found between tissue pH at delivery and blood pH in the umbilical artery (r = 0.78) and vein (r = 0.67). In no case with normal tissue pH (more than 7.20) and abnormal CTG was the Apgar score less than 8 one minute after delivery. A normal tissue pH almost always means that the fetus is not asphyxiated, but a low tissue pH reading may be caused by other factors than acidosis of the fetus. Continuous pH monitoring during labor remains a research method.