Fetal Heart Signal Monitoring with Confidence Factor

In this paper we present a PDA-based fetal heart monitor that is able to provide instantaneous fetal heart rate (FHR) for the pregnant women. A modified spectral subtraction algorithm is first used to remove the unwanted stationary background noise from the noisy fetal heart sound. The AM/FM modulation technique is then employed to make the fetal heart sound more audible so that both pregnant women and gynaecologists can identify the rhythmic fetal heart beat sounds easily. A real-time algorithm is proposed to extract the fetal heart rate information from the weak and noisy signals. Furthermore, based on the signal spectrum distribution, a confidence factor (CF) is designed to indicate the reliability of the estimated fetal heart rate in real time. The device has been tested in a local hospital on a sample group of 41 pregnant women. Our finding shows that an approximate 75% of the pregnant mothers are able to hear their baby´s heart sound clearly using our device. Tests are also carried out to compare the fetal heart rate calculated using our device and the existing ultrasound cardiotocography (CTG) machine. In most time our device functions properly and provides results close to the CTG records