Labor and fetal heart rate decelerations: relation to fetal metabolic acidosis.

Although intrauterine fetal compromise during labor accounts for a small proportion of cerebral palsy cases, fetal hypoxic-ischemic encephalopathy remains an important and sometimes preventable etiology. This paper reviews the mechanisms regulating fetal heart rate responses, pathogenesis of fetal metabolic acidosis, and thresholds for metabolic acidosis associated with hypoxic-ischemic encephalopathy. The knowledge of normal changes in fetal metabolic acidosis during labor together with changes in association with fetal heart rate decelerations, can aid in the interpretation and management of fetal heart rate tracings.