External fetal heart monitoring is performed by attaching external transducers to the mother's abdomen with elastic straps.

External fetal heart monitoring is performed by attaching external transducers to the mother's abdomen with elastic straps. The transducers use Doppler ultrasound to detect fetal heart motion, and the information is sent to the fetal heart monitor which calculates and records the fetal heart rate on a continuous strip of paper. The typical fetal monitor strip consists of two rows of graphs; one charting the fetal heart rate (in beats per minute) and the other graph charting the mother's contractions (in mm of Hg).