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Aims: This study aimed to simplify fetal monitoring, reduce inter-observer differences and false-positive diagnosis and monitor a large number of births simultaneously. Methods: Fetal signals from several births were transmitted to a central computer via local area network (LAN) or telemetry and analyzed using a multichannel timesharing system. Fetal heart rate (FHR) abnormalities were detected by using three programs: the experts' knowledge system, power spectral analysis and artificial neural network. Abnormal results were automatically communicated directly to the attending doctor. Instead of an FHR chart recorder, the original fetal signals were stored on the computer and re-processed on demand. Results: a maximal FHR score in the first stage of labor indicated a low Apgar score, and correlated with umbilical blood pH. The fetal distress index derived from the FHR score was three or more in cases of fetal acidosis. The neural network yielded probabilities of fetal outcome that coincided with the FHR score, and the neural index derived from these probabilities predicted fetal outcome. Pathological sinusoidal FHR and severe loss of FHR variability were automatically diagnosed by power spectral analysis. Perinatal mortality was 1.1 in 1.000 births, which was significantly lower using this central computerized system than the previous system, and no cases of cerebral palsy were reported 2 months after delivery. Conclusion: The central computerized automated fetal monitoring system improved fetal outcomes even in institutions dealing with a large number of births.

A technique for realization of low-voltage OTAs is presented in this letter. A very low-voltage differential-output OTA is realized by employing a new common-mode amplifier in the common-mode feedback circuit. The results of PSpice simulations are shown. The proposed OTA can operate at a 0.9 V supply voltage.

Ultrasound fetal heart rate monitoring is very useful to determine the status of the fetus because it is noninvasive. In order to ensure the accuracy of the fetal heart rate (FHR) obtained from the ultrasound Doppler data, we measure the fetal electrocardiogram (ECG) directly and obtain the Doppler data simultaneously. The FHR differences of the Doppler data from the direct ECG data are concentrated at 0 bpm (beats per minute), and are practically symmetrical. The distribution is found to be very close to the Student's t distribution by the test of goodness of fit with the chi-square test. The spectral density of the FHR differences shows the white noise spectrum without any dominant peaks. Furthermore, the f-n(n>1) fluctuation is observed both with the ultrasound Doppler FHR and with the direct ECG FHR. Thus, it is confirmed that the FHR observation and observation of the f-n(n>1) fluctuation using the ultrasound Doppler FHR are as useful as the direct ECG.

A Cohen's class time-frequency (TF) distribution has high resolution in time and frequency simultaneously on a TF plane. It is a powerful tool for nonstationary signal analysis of the type observed commonly in speech and biological signals. A kernel of high resolution was investigated for its applicability to biological signals. To apply the TF analysis with the new kernel to the analysis of a signal from a blood flow, an ultrasound Doppler sinusoidal shift signal was studied. Experimental data were obtained in olive oil by moving a steel ball to and fro by continuously irradiating it with ultrasound. The movement of the steel ball was controlled by various functions. Three kernels were used: (1) a Wigner kernel, (2) a Choi-Williams kernel, and (3) our new kernel. The demodulation accuracy with our new kernel was higher and negative components were smaller than with the Choi-Williams kernel.

To estimate the measurement error in an ultrasound fetal heart rate (FHR) monitor, we compared the differences in the distribution of the FHR measured with an ultrasound Doppler to the FHR measured with a direct fetal electrocardiogram. We confirm that (1) the distribution is very similar to Student's t distribution, and (2) the number of degrees of freedom in Student's t distribution has a significant impact on the evaluation of fit.

Frequency fluctuations of 5-MHz, 5th-overtone, piano-convex AT- and IT-cut quartz oscillators were measured with reference to a Cs oscillator (HP 5061A) while the oscillators were kept in a temperature-stabilized oven at Fourier frequencies from 10-2Hz down to 10-6Hz. A power spectral density of the frequency fluctuation consists of three parts due to dependence on the Fourier frequency f, which are proportional to 1/f2, 1/fand to f0. The parts in proportion to 1/f2and f0are found to be related to the temperature fluctuation through static and dynamic temperature coefficients of the oscillation frequency. However, the 1/fpart is found to be uncorrelated to the temperature fluctuation.