Fetal heart rate patterns, perinatal asphyxia, and brain injury

Hypoxic-ischemic injury, occurring during the intrapartum period, remains the most controversial perinatal cause of central nervous system injury. Current evidence suggests that injury during the intrapartum period is uncommon. The most widely used technique for antenatal surveillance is fetal heart rate monitoring. Fetal heart rate abnormalities, however, are infrequently associated with long-term adverse outcomes. Fetuses may manifest many minutes of "ominous" fetal heart rate patterns without evidence of irreversible central nervous system injury. Neurologically abnormal fetuses also may manifest abnormal fetal heart rate patterns because of neural mechanisms controlling heart rate, rather than because of intrapartum hypoxic events. Fetal acidosis also correlates poorly with outcome. The conclusion that a child's neurologic abnormalities are due to brain injury occurring during the intrapartum period cannot be based on fetal surveillance findings in isolation, but must be based on the consideration of many parameters.