Novel Acoustic Monitor Records Fetal Heart Rate

A new type of home fetal heart rate (FHR) monitor, based on a two-microphone system, could save the lives of unborn infants in complicated pregnancies.

Researchers from the Manoharbhai Patel Institute of Engineering & Technology (Gondia, Maharashtra, India; www.mietgondia.com) developed a computer simulation model of a potential novel fetal home monitoring application that could also be helpful in the management of complex pregnancies. The device is based on two small acoustic sensors that monitor FHR and feed the information to a wave analyzer, which is connected to a bedside personal computer (PC) with internet access.

The first microphone is attached to the mother's abdomen to pick up the sound of the fetus' heartbeat, and the second is attached at a reasonable distance to pick up ambient noise. A software algorithm then subtracts the "noise” channel from the fetal sound to produce a waveform (WAV) file that can be further analyzed for medical anomalies; if a problem is identified, the WAV file can be compressed to an MP3 file format for rapid upload via the internet to the physician's computer, and trigger a warning to the mother to seek medical assistance. The study describing the FHR model was published in the August 2009 issue of the International Journal of Engineering Systems Modeling and Simulation.

"Monitoring FHR during a woman's most restful hours at home and providing urgent medical assistance in case of abnormality will prove to be very effective in the prevention of stillbirth and other prenatal complexities,” concluded lead author A.K. Mittra, Ph.D., an assistant professor in the electronics engineering department. "Simulation results show that the technique is suitable and effective for long-term FHR home monitoring.”

The sound of FHR is asynchronous and different from the maternal pulse, and can be detected and heard in the nearby uterine arteries. The variation in the FHR is one of the most important approaches in fetal surveillance. In hospitals, ultrasound-based equipment such as the Doppler fetal monitor and the cardiotocograph (CTG) are used for FHR monitoring. However, recent studies have shown that frequent exposure to ultrasound radiation is not recommended for fetal well-being, and is therefore not recommended for prolonged monitoring applications.

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Manoharbhai Patel Institute of Engineering & Technology