A technique was developed that could allow expectant parents to hear their baby’s heartbeat continuously at home with a non-invasive and safe device that is potentially more accurate than any fetal heartrate monitor currently available in the market.
The device, which uses the same commercial sensors used in smartphones to horizontally or vertically orient the device, can record vibrations sent through a mother’s abdomen when her baby’s heart beats or when the fetus squirms and kicks.
Many stillbirths are preceded by variations in fetal movement and heartrate, so affordable, lightweight monitors that detect vibrations generated from a heartbeat could be worn continuously in the final weeks of pregnancy to ensure that distressed fetuses receive prompt medical attention.
In experiments on ten pregnant women, the device detected fetal heartrate with about the same accuracy as fetal cardiotocograms (f-CTG), which measure the baby’s heart electrical activity (ECG) together with the mother’s uterine contractions.
A vibration monitor offers important advantages over existing tools based on ECG or Doppler ultrasound technology, which require specialized knowledge to use and can be bulky and expensive. The new sensors are barely a fifth of an inch long and can run off a 3-volt battery for more than 24 hours. Signals from three different sensors were combined and algorithms were used to isolate the fetal heartbeat.
The new monitor also poses no risk to the fetus — a concern with ultrasound monitors that can heat tissue if used continuously for long periods. The new monitor simply detects existing vibrations, like a doctor listening with a stethoscope. Vibration monitors can also offer an objective measure of fetal movement, which is currently assessed simply by asking moms to count the times their baby kicks.