14-1
FM5000C - FM5000PLUS
Maternal/Fetal Monitor
User Manual
Chapter 14 Fetus Monitoring
There are two basic types of fetus monitors: antepartum monitor for pre-delivery use and intrapartum
monitor for in-delivery use. The antepartum monitor does not have the internal monitoring ability and thus can
not monitor the fetal heart rate(FHR) directly through the fetus scalp electrode or monitor the internal uterine
pressure (IUP) of the mother through the internal pressure pipe. It monitors the FHR by connecting the
ultrasound transducer to the mother’s abdomen and monitors the uterine pressure by connecting the TOCO
Transducer to the bottom of the mother’s uterus.
14.1 Difference between Antepartum and Intrapartum Monitor
The antepartum monitor ensures the accuracy and reliability for FHR measuring by using the high-sensitivity
ultrasound transducer, high-performance signal processing circuit and advanced FHR calculation method.
The intrapartum monitor is acceptable to few pregnant women as it is not easy to operate, not cost effective
(use one-off electrode or pressure pipe) and likely to cause trauma to the patient.
14.1.1
Antepartum Monitoring Principles
Below is the ultrasound Doppler FHR monitoring principles:
The Doppler FHR monitoring is supported by the Doppler Effect. The ultrasound wave will be
reflected when meeting any obstacle in the propagation process. If the obstacle is still, the reflection frequency
will be identical with the transmitting frequency. If the obstacle moves, the reflection frequency
will change: become higher (or lower) when the obstacle faces the sound source with the front (or back). The
faster the obstacle moves, the greater change the reflection frequency will experience. That is the Doppler
Effect. In clinical application, the ultrasound transducer is used to transmit the ultrasound wave into the human
body. When the ultrasound wave meets any locomotive organ (like heart), the echo signals will be
changed and processed to collect the heart rate information which indicates the heart activities.
It is the best time to do the Doppler FHR monitoring when the fetus faces the mother’s abdomen with the back.
If the fetus faces the mother’s abdomen with the front, his/her arms and legs will impact the echo signals.
When the fetus turns, his/her heart will deviate from the irradiation area of the transducer to cause
weaker echo signals and reduced Doppler Effect.
14.1.2
Terms about Monitor
Continuous wave working mode: the receiver and transmitter of the ultrasound transducer work
