[A study of the cardiotocograms recorded by a separated 1MHz ultrasound transducer]

Fetal heart rate records were obtained in 12 antepartum and 13 intrapartum cases, with an ultrasonic Doppler transducer with five separated crystals and a conventional transducer. The loss of the FHR record due to increased noise in 30 minutes before delivery ranged from 1.1 to 23.2% (6.4 +/- 6.5%) in the separate type transducer, and it was 0.6 to 29.9% (10.5 +/- 7.6%) in the conventional one. During the 5 minutes before delivery, it was 3.3 to 58.0% (20.2 +/- 18.5%) in the separate type, and 3.3 to 70.0% (31.6 +/- 19.5%) in the conventional one. Clearer FHR records were obtained with the use of the separate type than the conventional one (p less than 0.05). Noise was mostly recorded in the 5 minutes before delivery. In the NST, the loss of the FHR record due to maternal posture change decreased when the new transducer (p less than 0.05) was used. The loss was 0 to 56.7% (14.9 +/- 18.2%) with the new type, and 2.0 to 100% (42.9 +/- 36.4%) with the conventional one for the maternal posture which showed the worst record. By using the separate type transducer, maternal posture need not to be limited in the NST, and the somatic and mental discomfort is less than when the conventional one is used.