Finding a passive way to measure Foetal Heartbeats

Paul Teal has recently featured in the Dominion for his research on developing a less invasive way of monitoring foetal heart beats. Senior Lecturer Paul Teal says his aim is to find a more passive method of determining the heart beat of infants in the womb than the active method currently used by physicians and midwives.

“A popular method used in New Zealand is the SonicAid, which is a Doppler device that puts an ultrasound pulse into the mother. You can tell what the heart is doing from the change in frequency of the reflected sound.”

Paul says most clinicians believe that Doppler ultrasound is perfectly safe, but anecdotal evidence suggests many mothers don't like this method, as it actively puts energy into their bodies, and many midwives report that babies aren't too keen on it either.

“So I've been looking at a passive way to measure the foetal heart rate. You can do this either by putting electrodes on the mother and then detecting the Electric Cardiogram (ECG) signal, or by listening with microphones, which is what my research has focused on. This is more like using the Pinard – the foetal stethoscope that midwives used before the invention of Doppler ultrasound, but much more reliable and easy to use.”

Paul, who previously worked at Industrial Research Limited (IRL) in Gracefield, has been collaborating with his former colleagues to develop a method of using microphones to separate out the mixture of signals emitted from the womb by using a technique called Blind Source Separation.

“This isolates the foetal heart rate from the mother's heart rate, and the background noise. It's also a more passive method of monitoring that doesn't negatively impact upon either the mother or the baby.”

Paul says he and his IRL counterparts are now working closely with Wellington midwives to collect data from mothers using this less invasive method.

“We've proved the method works in the last few weeks of pregnancy, but we're hopeful that eventually we will be able to use it from when a foetus is 18 weeks. Doppler ultrasound can work from about 12-14 weeks, but the important stages are later in the pregnancy.”