An Improved Method of Long-Term Fetal Heart Sound Monitoring in High-Risk Pregnancies

Abstract

Current method for Fetal Heart Rate (FHR) monitoring relies heavily on Ultrasound Techniques. This has two important disadvantages; firstly, there are significant chances that long-term exposure to ultrasound may harm the unborn, and secondly, the ultrasound machines and its trained operators would prove to be an expensive proposition and could not be utilized for longer period of time. Because of these reasons, the existing instruments are not suitable for carrying out frequent and long-term measurement of FHR, which is highly recommended in high-risk pregnancies.In this paper an alternative method for long-term FHR monitoring is proposed. With the help of a designed acoustic cone, sound wave guide and piezoelectric sensor, acoustic energy produced by fetal heart movement is detected from subject’s (mother’s) abdomen. An additional microphone is used to detect ambient noise, which will be used for adaptive digital filtering and noise cancellation from fetal heart sound wave. Both signals are subsequently filtered, amplified and recorded in a two-channel removable memory device. All these components were assembled in a low power portable electronic instrument to allow long term fetal surveillance. Later on, the recorded data is transferred to a personal computer where it is further digitized, filtered, analyzed and displayed. The designed instrument has been examined and tested in Government Hospital on women with gestation age between 28 to 41 weeks. The results showed that the technique is suitable and effective for long-term fetal heart sound monitoring.