Evaluation of fetal and neonatal acid-base status.

Determination of fetal acid-base status, either at birth, intrapartum, or antepartum, is the gold standard for the diagnosis of fetal asphyxia. Indirect methods such as Apgar scores and fetal heart rate monitoring show at best only minimal correlation. It is evident that intrauterine hypoxia is a rare cause of central nervous system injury, and the finding of a normal acid-base status at birth should lead the clinician to search for other causes of central nervous system injury or birth depression. A combination of techniques including fetal acid-base assessment, electronic fetal heart rate monitoring, and thorough neonatal evaluation probably provides the best predictor of long-term outcome. Newer methods of umbilical cord sampling and acid-base determinations in the intrauterine growth retarded fetus hold some hope for the future.