Researchers have developed a technique that can accurately separate foetal heartbeat from background noise in acoustic recordings, a finding that could potentially lead to cheap and non-invasive foetal monitoring while making pregnancy much safer.

The new technique involves doctors examining the sounds in a mother's abdomen, by placing cheap vibration sensors on the mother's belly and recording the acoustic signals emitted by the foetal heart. In fact, it is simple enough so that a mother could potentially place the sensors on her belly in the comfort of her home and make recordings that her doctor can analyse later, the researchers said."Our work suggests that there is potential for low cost and continuous recordings of foetal heart sounds in the home... Our results should help doctors to make pregnancy safer," said Elisavet Koutsiana, a researcher at the Aristotle University of Thessaloniki in Greece.

So far, the low acoustic energy of the foetal heartbeat, along with conflicting sounds such as the mother's own heartbeat and breathing and noise from her digestive system had made it difficult to accurately pick out the sound of the foetal heart from the recording. For the study, published in the journal Frontiers in Bioengineering and Biotechnology, the team used mathematical analysis technique called Wavelet Transform-Fractal Dimension -- to de-noise lung and bowel sounds.

The researchers could clearly discern the foetal heart sounds in both authentic foetal recordings and simulations of healthy hearts, and only slightly less clearly in simulations of abnormally fast or slow heartbeats.They could still recognise the heart sounds even when unexpected noises were present. Further, they could also distinguish between the different segments of the foetal heartbeat, which could be useful for doctors in their assessment of foetal health.