Abstract: A device and method for monitoring over a period of time a foetus in a pregnant mammalian animal. A piezoelectric synthetic plastics material detector is applied to the abdomen of the pregnant animal and produces an electrical signal as a result of foetal activity such as foetal body movement, breathing movement and heart rate. This signal is received in receiver means and is compared with previously determined signals characteristic of various types of foetal activity. Output means produce an output indicative of the activities of the foetus over the monitored period from which can be gauged foetal development and/or well being.