Analysis of Heart Rate Variability of the Fetus during Delivery

Prof. Shimon Abboud
Department of Biomedical Engineering
Fleischman Faculty of Engineering, Tel Aviv University
Prof. Shlomo Mashiah
Department of Obstetrics and Gynecology, Sheba Medical Center,
and Sackler School of Medicine, Tel Aviv University

Fetal heart rate (FHR) variability is related to fetal condition including transient or permanent abnormalities of rhythm and parameters for assessment of fetal hypoxemia or acidosis. Loss of the variability in the FHR is generally felt to be negative findings regarding fetal well being. On the other hand, presence of reasonable FHR variability generally is equated with a functional responsive fetal autonomic nervous system.

The present study has two objectives:
• To correlates the time and frequency domains fetal heart rate variability with indices of fetal well being during delivery.
• To investigate the accuracy of the fetal heart rate variability parameters obtained with ultrasound techniques

Simultaneous recordings of the scalp fetal ECG and the Doppler signal from an ultrasound transducer are performed for 30 minutes during delivery.
The scalp ECG and the Doppler signal are digitized at a sampling rate of 1 kHz with 16 bits analog to digital converter and stored on the hard disk of the computer for future analysis.

Peak detection algorithm is used to determine the heart rate signal. Heart rate variability obtained from the scalp ECG and from the ultrasound signal are calculated and compared using time and frequency domain procedures. The average and standard deviation of the heart rate signal and the power in the low and high frequency ranges from the spectrum of the HR signal are compared. The heart rate variability parameters obtained are correlated with indices for fetal well being.