Fetal heart rate (HR) and rhythm can be determined using M mode echocardiography or via ECG monitoring. For the latter, electrodes are placed dorsal and ventral to the fetus and simultaneously cranial and caudal to the mare's heart. Using appropriate software, the fetal signal can be subtracted from the combined mare and fetus trace to generate a fetal ECG. Technical challenges include maintaining electrodes in position, reduced quality in response to fetal movement, and limited ability to separate maternal and fetal traces if HR are similar. The fetal HR should decline from around 120bpm at 7 months, towards around 80 bpm at term. The fetal HR should increase in response to movement. In response to fetal hypoxia, there is a reduction in HR and lack of episodic HR increases. With progressive compromise, there may be persistent tachycardia and finally bradycardia and cardiac arrest. Single spot measurements are not as useful as measuring HR progressively over time. Although the technique has much promise, there is a need to accumulate clinical data to understand fetal HR responses better and to determine how best to intervene when fetal compromise is identified.