Computer interpreted fetal electroencephalogram. I. Relative frequency of patterns.

Fetal electroencephalography (FEEG) is a clinical research technique for monitoring the electrical activity of the fetal brain during labor. Because of the massive volume of data, it has not previously been practicable to quantify the frequency of occurrence of the various patterns by visual analysis. With the use of a computer program, which has been shown to be consistent with visual interpretations, records for 11 fetuses, known to be neurologically normal at 1 year of age, were analyzed. Adequate FEEG had been recorded 73.6 per cent of the time during which the fetuses were monitored. In 10,511 10 second epochs of adequate FEEG, the Mixed pattern was found to be dominant, with a relative frequency of 41.2 per cent. The relative frequencies of Trace Alternant and High Voltage Slow activity were 32.3 per cent and 21.5 per cent, respectively. Low Voltage Irregular, Voltage Depression, and Isoelectricity occurred infrequently, accounting for approximately 4.6 per cent of the epochs. The relative frequencies of the various patterns were stable from the onset of monitoring of FEEG through neonatal EEG obtained in the delivery room. These data will form the basis for subsequent studies of FEEG changes associated with various endogenous and exogenous factors.