The maternal ECG (MECG) is the main source of interference in fetal ECG (FECG) monitoring. The MECG is detected at all electrodes placed on the mother's skin (thoracic and abdominal). In the case of multi-fetal pregnancies the traditional adaptive filtering technique provides a "maternal clean" signal consisting of the two fetal ECG signals. It cannot however provide the desired individual FECG. The work reported here suggests the use of the blind source separation (BSS) algorithm to deal with the problem. Simulation studies show that the BSS algorithm can perform a separation of twins' FECG. Real signals were recorded from pregnant women at their 28-30/sup th/ week of pregnancy, carrying 2-3 fetuses. The noise was found to be too strong for the algorithm (and the naked eye) to notice any fetal heart signal.