IMPROVEMENTS IN COMPUTERIZED FETAL HEART-RATE ANALYSIS ANTEPARTUM

The continued development of a computerised system for measuring the p attern of the antepartum fetal heart rate (FHR) is described. Previous work had established that measurement of FHR variation objectively de tects chronic fetal hypoxaemia and the onset of metabolic acidaemia an tepartum. The normal centiles were calculated for the amplitude of lon g-term FHR variation, in episodes of high and low variation. week by w eek from 24-42 weeks gestation. Reference to these (automatically by t he computer) improved discrimination between normal and questionable r ecords in 38% of records, with a small saving of time. Two types of si nusoidal rhythm were described (slow, 1 in 2-5 minutes, incidence 0.16 % of subjects, and faster, 2-5 per minute, incidence 0.025%) with meth ods for their detection. Both may be of sufficient amplitude to induce an episode of high FHR variation. The different effects of maternal s teroid (betamethasone or dexamethasone) administration of FHR variatio n were compared, and the clinical consequences considered. The frequen cy distribution of basal FHR in normal and abnormal records was measur ed, and the effects on basal FMR outside the normal range (120-160 bpm ) on FMR variation described. Adjustment of the FHR baseline was under taken when, exceptionally, large abrupt changes in heart rate occurred during a record. The duration and frequency of FHR record acquisition in clinical practice were reviewed, and new policies recommended. Wit h adequate safeguards, measurement by a computer offers reliable objec tive information from which fetal health may be assessed, more objecti vely and accurately than by visual inspection.