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Wearable Motion Sensors Could Reduce Stillbirths

A milestone in any pregnancy is the thumping sound of a baby's heartbeat. At present, a team of scientists at Stevens Institute of Technology have formulated a method that could enable expectant parents to hear their baby's heartbeat continuously at home with a non-invasive and safe device. This device is said to be potentially more accurate than any commercially available fetal heart rate monitor in the market.

The device comprises the same commercial sensors used in smartphones to vertically or horizontally orient the device, and can record vibrations transmitted through a mother's abdomen when her baby's heartbeats or when the fetus kicks and squirms. Praised by physicians, the device could possibly decrease an estimated 2.6 million stillbirths per year around the world.

Almost a third of stillbirths occur in the absence of complicating factors. Our device could let a pregnant woman know if her fetus is compromised and she needs to go to the doctor.

Negar Tavassolian, Study Lead and Associate Professor, Stevens Institute of Technology

A number of stillbirths are preceded by differences in fetal movement and heart rate, so reasonably priced, lightweight monitors that detect vibrations produced from a heartbeat could be worn continuously in the final weeks of pregnancy to guarantee that distressed fetuses receive quick medical attention. The research paper has been published in the July 24th early access issue of IEEE Sensors Journal.

Tavassolian and first author Chenxi Yang, a graduate student at Stevens, partnered with Bruce Young and Clarel Antoine, two OB-GYNs at New York University-Langone Medical Center to test their sensors. In experiments involving 10 pregnant women, they learned that the device could detect fetal heart rate with nearly the same accuracy as fetal cardiotocograms (f-CTG), which computes the baby's heart electrical activity (ECG) along with mother's uterine contractions—and said to be the present standard for fetal monitoring.

A vibration monitor offers essential benefits compared to present-day tools based on ECG or Doppler ultrasound technology, which require expert knowledge to use, and can be bulky and expensive. One leading commercial monitor system currently available weighs over 11 pounds and has a battery life of four hours; by contrast, the Stevens team's sensors are hardly a fifth-of-an-inch long, weigh virtually nothing, and can work using a 3-volt battery for over 24 hours.

Yang's earlier work has demonstrated that chest vibrations could be used to monitor an adult's heartbeat, but measuring the fetal heartbeat is an order of magnitude tougher, with the feeble vibrations of the fetus's minute heart muffled by the maternal host’s movements. To solve that issue, the Stevens team integrated signals from three different sensors, and used algorithms to separate the fetal heartbeat.

The new monitor also poses no danger to the fetus—an apprehension with ultrasound monitors, which can heat tissue if used continuously for extended periods. The monitor built by the team simply detects current vibrations, similar to a doctor listening with a stethoscope.

Our monitors are completely passive, so there's no health concern.

Negar Tavassolian, Study Lead and Associate Professor, Stevens Institute of Technology

Vibration monitors can also deliver an objective measure of fetal movement, which is presently assessed just by asking moms to count the number of times the baby kicks. Integrating heart rate and movement data could offer critical insights into fetal health, exceeding anything that is presently available, Yang explained.

That's the big plan—to fuse these different modalities into a single device.

Chenxi Yang, Study First Author and Graduate Student, Stevens Institute of Technology

The present device uses sensors available in the market, but the long-term goal is to patent and market a tailored device. Costing much less than equivalent ultrasound systems or ECG, such a device could capture a major share of the worldwide market for fetal monitors, which is estimated to touch $3.6 billion by 2022.

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