INTERNAL / DIRECT:
Internal fetal monitoring is accomplished with a fetal scalp electrode that is a direct electrocardiogram of the FHR and therefore produces the most accurate FHR tracing having an advantage over the external monitoring. The FSE is attached to the fetus during a vaginal exam and then connected to a fetal monitor. Because the risk of transmission to the fetus is increased by the small puncture in the fetal scalp, use of internal scalp electrodes should be avoided if at all possible in the presence of known maternal infections such as HIV, hepatitis or GBS. Fetal scalp monitors are also avoided in preterm infants because of the increased risk of ventricular hemorrhage.
Electronic monitoring of UCs can be done internally by using an intrauterine pressure catheter (IUPC). It is inserted into the uterine cavity through the cervical os. It reflects the pressure inside the uterine cavity. As the pressure changes, it traces on the graph paper. The IUPC can measure the resting tone of the uterus between contractions, referred to as intensity. An advantage of an IUPC is that it provides a near-exact pressure measurement for contraction intensity and uterine resting tone. The sensitivity of the IUPC allows for very accurate timing of UCs, thus making it extremely useful when closer uterine monitoring is needed. A disadvantage for both internal monitoring methods is that membranes must be ruptured and adequate cervical dilation must be achieved for insertion. The procedure is invasive and increases the risk of uterine infection or perforation or trauma. It can also cause a placenta rupture if the placenta is low-lying.
EXTERNAL / INDIRECT:
Electronic FHR monitoring can be done externally by using an ultrasound (US) transducer. The transducer is placed on the maternal abdomen over the fetal back and held by an elastic belt. The US transducer