AWHONN Fetal Heart Monitoring Exam
| Basic Concepts with Questions and
Verified Answers| Latest 2024/2025
Guide
Name the 4 types of decelerations of FHR
- Correct Answer - Early
Late
Variable
Prolonged
Define early deceleration
- Correct Answer - Visually apparent, usually symmetrical, gradual
decrease (>30 seconds from onset to nadir), and return of the FHR
associated with a contraction. The nadir is typically coincident with the
peak of the contractions, giving a mirror image appearance. They begin
early in the contraction, reach their lowest point at the peak of the
contraction and return to baseline at the end of the contraction. Usually
due to pressure on the fetal head from contractions. They cause
changes in intracranial pressure and cerebral blood flow, which
stimulates the vagus nerve. They are a normal reflex response.
Early decelerations drop below baseline by how many BPM?
- Correct Answer - No more than 20-30 BPM and rarely below 100-110
BPM
Define a late deceleration
,- Correct Answer - Shaped like an early decel-visually apparent, usually
symmetrical, gradual decrease and return of the FHR associated with a
contraction
-the lowest point of the decel will occur after the peak of the contraction.
They dip no more than 30-40 BPM below the baseline. This does not tell
the degree of hypoxia.
What are late decels with absent variability predictive of?
- Correct Answer - Abnormal fetal acid-base status and require an
evaluation and prompt intervention.
What are variable decelerations?
- Correct Answer - May be periodic or episodic, the most common
pattern seen during labor. Their shape and depth are variable, not like
early or late's, rarely smooth and regular.
A visually apparent abrupt decrease in FHR from onset of decel to nadir
of <30 seconds. The decrease is >15 BPM lasting >15 seconds and < 2
minutes in duration.
Usually assoc. with cord compression, fetal baroreceptors increase the
FHR to maintain cardiac output.
Define prolonged deceleration of the FHR.
- Correct Answer - A decrease in FHR of > 15 BPM lasting > 2 min but <
10min from onset to return to baseline.
Any decel longer than >10 min is a baseline change.
Prolonged decels are due to a sudden significant change in the fetal
environment rather than a repetitive stimulus. Immediate communication/
intervention is necessary.
,True or False
A preterm fetus my be more susceptible to hypoxemia
- Correct Answer - true
True or False
The nervous system is not fully developed in fetuses prior to 32 wks
gest. - Correct Answer - true
What are the different characteristics of a fetus prior to 32 wks gest. than
a term fetus? - Correct Answer - 1. Higher baseline FHR
i.e. a 23 wk gest may have a baseline of 155 BPM but at term, the same
baby may have a baseline of 130 BPM.
Any baseline above 160 BPM is still considered tachycardia.
2. Decreased variability
bc the central nervous system is not fully developed, variability may be
decreased.
3. lower amplitude accels in preterm (before 32 wks) accels of at least
10 BPM above baseline for at least 10 sec is acceptable.
4. more frequent occurrences of variable decels
When should an IUPC (intrauterine pressure catheter) be placed?
- Correct Answer - When information can not be obtained by palpation
or use of toco and if there are no contraindications to its use.
i.e. increasing oxytocin w/ elevated BMI if contractions are not being
detected using toco.
Who may insert an IUPC?
- Correct Answer - The primary obstetric provider.
Identify the 4 types of electronic instrumentation used to assess FHR
and uterine activity.
- Correct Answer - External-
Doppler ultrasound transducer (converts movement into sound to
tracing on paper)
Tocodynamometer (TOCO) monitors externally contractions.
Internal-
Fetal Spiral Electrode (FSE) monitors internally FHR.
Intrauterine pressure catheter (IUPC) monitors internally contractions.
Explain the principles of the Doppler shift as related to FHR monitoring.
- Correct Answer - If the reflecting surface is moving the reflected signal
has a frequency change known as a doppler shift.
If the reflecting surface is moving toward the signal source the frequency
of the signal increases; if the frequency decreases the surface is moving
away. The back and forth movement of the fetal myocardium will
produce an alternately higher and lower frequency.
Stationary surfaces undergo no frequency change. The US ignores all
reflected signals that have the same frequency as the transmitted signal.
Those signals that have undergone a frequency change - a Doppler
shift- are converted into electronic signals.
List the 4 steps in using the external ultrasound device.
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