Assessment of foetal cardiac function is more challenging than in the adult, in whom emerging technologies are tested. The postnatal cardio-respiratory interaction is replaced by the cardio-placental circulation and impedance of the brain, and distal vascular beds play an important role in modulating flow to enable its redistribution in the foetal body. Prenatal specialists, comprising obstetricians and cardiologists, have tested a variety of traditional methodologies, as well as non-Doppler offline ultrasound methods in the foetus. This article reviews the development of techniques, outlines their use, and draws attention to pitfalls in adapting technologies validated in the adult heart to the small, fast beating, remote, and largely ungated foetal heart.