5.14 Detection of cardiovascular compromise in the fetus
Assessment of cardiac function is a useful technique for monitoring the well-being of the fetus. The technique is poorly developed at present but offers potential for future use. Transabdomenal ultrasonography can be used for monitoring fetal heart rate by placing the M-mode cursor through the fetal heart and calculating the rate from the M-mode trace. A persistent tachycardia (> 120 bpm in a near-term fetus) or bradycardia (<70 bpm), a fixed heart rate, or arrhythmias, are suggestive of fetal distress. The advantage of the ultrasound technique is that the fetal fluids and fetal position can also be assessed.
Fetal electrocardiography can be used to monitor fetal heart rate and docuthe presence of a live fetus. A bipolar lead system is used, with the leads placed in either a ventrodorsal configuration or from one flank to the other. Small complexes will be seen superimposed on the normal ECG of the dam. Good electrical contact must be maintained in order to avoid artefact obscuring the fetal trace.