The aim of this study, is to determine whether the fine characteristics of the fetal heart sounds could be used to identify intrauterine growth retarded fetuses. A preliminary evaluation, was conducted to compare these characteristics between intrauterine growth retarded fetuses and normal fetuses in the antenatal period after 36 weeks of gestation. Altogether, 7 IUGR fetuses were compared with 12 normal fetuses. An instrument named the Fetal Frequency Phonocardiogram was designed for this purpose. When connected to a personal computer and with a software programme specially written, the fetal heart sound characteristics were analysed. After detailed analysis, there were 3 significant differences between IUGR and normal fetuses, all of which gave a p-value of < 0.01. The frequency of the first heart sound was significantly higher in the IUGR fetuses compared to normal fetuses. The ratio of the amplitude of the first heart sound over the second heart sound was higher in the IUGR group. Finally, the ratio of the time between the first and second heart sound over the cardiac cycle was shorter in the IUGR fetuses. Fetal heart sound analysis, may provide a simple non-invasive method of detecting and monitoring fetuses at risk in the antenatal period.