“…However, the tech nique cannot distinguish between acute failure of placental perfusion and consequent respiratory acidosis due to hypercapnia (for example, the result of maternal hypotension) and chronic interference with fetal oxygenation which leads to more serious metabolic acidosis (Takemura, 1973). Occasionally simultaneous measurement of maternal pH (or, ideally, the maternofetal base deficit difference) will be needed to exclude an in fusion acidosis of the fetus of maternal origin (Roversi et al, 1975). In practical terms, however, careful assessment of the FHR trace with reference to the duration and type of abnormality seen, and its rate of deterioration or recovery, can usually suggest the appropriate etiology of a fall in pH.…”