basic fetal monitoring review

Basic Fetal MonitoringReview

Ana H. Corona, FNP-CNursing Instructor

February 2009

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Electronic Fetal Monitoring

• Definition of fetal monitoring– Method of assessing fetal status before

and during labor• Why is fetal monitoring important

– To provide insight that may affect fetal outcomes

• Information is recorded on graph paper • Information is permanent part of the

maternal medical record• Information is retrievable for litigation

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Normal Assessment Findings

• FHR between 110-160 in gestations 32-40+ weeks– Rates slightly above 160 are normal in

gestations less than 32 weeks.

• Regular rhythm

• Increases in the FHR associated with fetal movement that return to original rate range

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Electronic Fetal Monitoring Clarification

• Information for students is for educational purposes only

• Students should not assume any responsibility for interpretation of fetal monitor tracings

• It takes months to years of experience to be prepared to interpret fetal monitor tracings

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Methods of Electronic Fetal Monitoring

• External– Noninvasive method– Utilizes an

ultrasonic transducer to monitor the fetal heart

– Utilizes the tocodynamometer (toco) to monitor uterine contraction pattern

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Methods of Electronic Fetal Monitoring

• Internal Fetal Monitoring– Invasive– FHR is monitored via a

fetal scalp electrode– Uterine activity is

monitored by an intrauterine pressure catheter (IUPC)

• A combination of external and internal fetal monitoring is common practice

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Advantages and Disadvantages of Internal Fetal Monitoring

• Advantages– Patient can move without much interference in data

transmission– More accurate measurement of data– Data less likely to be affected by artifact

• Disadvantages– Invasive– Membranes have to be ruptured and cervix dilated– Application requires more skill– Procedure is uncomfortable for the mother– Risk of trauma and infection for mother and fetus

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Components of the Fetal Monitor Paper Tracing

• Strip has two components• Upper graph - records FHR data• Small squares represent 10 bpm

increases as well as 10 seconds duration • Lower graph records contraction data• Small squares represent 10 second

duration or 10 mmHg intensity – Dark line to dark line represents one

minute of time

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Baseline FHR

• Normal baseline FHR in a term fetus 37 completed weeks or more is 110-160 bpm.

– Determination of the baseline FHR is done between contractions

– Baseline is rounded in increments of 5 bpm example; if the FHR is running 125-135 then the baseline FHR should be documented as 130

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FHR Variability

• Normal changes and fluctuations in the FHR over time.

• Best assessed between contractions

• Considered to be the best indicator of fetal well-being

• Variability can be influenced by hypoxic events, maternal hemodynamic issues, drugs, etc.

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Examples of Variability

• Absent: Not detectable from baseline

• Minimal: Less than 5 bpm from baseline

– May occur with:

– normal fetal sleep patterns

– mother has received analgesia for pain

• Moderate : 6-25 bpm from baseline (optimal pattern)

• Marked: More than 25 bpm from baseline

How Do Uterine Contractions Affect Fetal Heart Rate?  • Can affect FHR by increasing or decreasing the rate in

association with any given contraction. • 3 primary mechanisms by which UCs can cause a

decrease in FHR 1.          Fetal head 2.          Umbilical cord3.          Uterine myometrial vessels

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Periodic and Episodic FHR Characteristics

• Periodic: Refers to changes in the FHR that occur with or in relationship to contractions

• Episodic: Refers to changes in the FHR that occur independent of contractions

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Examples of Periodic Changes

• Variable decelerations: Result from some type of cord compression.– Nuchal cord, True knot– Decreased amniotic fluid

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Severe Variable DecelerationsNote the depth from the baseline

Baseline

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Early Deceleration

• Occur as a result of vagal stimulation to the fetal head during contractions which push the fetal head toward the pelvis.

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Late Decelerations

• Occur in response to utero-placental insufficiency. Blood flow to the fetus is compromised and there is less oxygen available to the fetus)

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Late Decelerations with Absent Variability

• Note the smoothness of the FHR pattern

• Decreased FHR caused by utero-placental insufficiency

• Compromised blood flow to fetus

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Prolonged Deceleration

• Deceleration of the FHR from the baseline lasting more than 2 minutes but less than 10 minutes.

• No explanation for why these occur

• Commonly associated with uterine hyperstimulation.

• Can also occur without any uterine activity

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Example Prolonged Deceleration• Note the duration of the deceleration lasts more

than 2 minutes.

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FHR Accelerations

• Are the most common type of FHR changes

• Are abrupt changes and will increase from the baseline 15 bpm lasting 15 seconds before return to the baseline in a healthy gestation more than 32 weeks.

• Less than 32 weeks increases of 10 bpm lasting 10 seconds are indication of a well oxygenated fetus.

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Example Accelerations• Note the increase from the fetal heart baseline

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Sinusoidal Pattern• Persistent wave variation of the baseline only seen

in about 2% of patients.• Related to severe fetal anemia, hypoxia, or

acidosis.

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Uterine Activity Assessment

• Periodic tightening and relaxing of the uterine muscle.

• Pituitary gland is triggered to release a hormone called oxytocin that stimulates the uterine tightening.

• Difference in Braxton Hicks contractions and true labor is the strength of the contractions and the changes in the cervix.

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Characteristics of Contractions• Frequency: How often they occur? They are

timed from the beginning of a contraction to the beginning of the next contraction.

• Regularity: Is the pattern rhythmic?• Duration: From beginning to end - How long

does each contraction last?• Intensity: By palpation mild, moderate, or

strong.– By IUPC intensity in mmHg– Subjectively: Patient description

Uterine Contraction

Segments of Contractions

• Increment: Beginning, building of pressure• Acme: Most intense part of the contraction• Decrement: Diminishing of the contraction• Rest: Period of time between contractions

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Assessment of Contractions

• Palpation: Use the fingertips to palpate the fundus of the uterus– Mild: Uterus can be indented with gentle

pressure at peak of contraction– Moderate: Uterus can be indented with firm

pressure at peak of contraction– Strong: Uterus feels firm and cannot be

indented during peak of contraction

Variable decelerations in FHR during labor are severe dips occurring at the peak of contraction. This FHR problem is associated with which one of the following conditions?

1. Utero-placental insufficiency

2. Fetal head compression

3. Uterine insufficiency

4. Pressure on the umbilical cord

Answer is D

• These decelerations are common during labor.

• The FHR drops during the contraction resulting from stimulation from chemoreceptors and baroreceptors as the cord is compressed.

• The nurse should recognize these readings on the fetal monitor as normal.

A nurse is caring for a client in labor and is monitoring the FHR patterns. The nurse notes the presence of episodic accelerations on the electronic fetal monitor tracing. Which of the

following actions is most appropriate?

1. Document the findings and tell the mother that the monitor indicates fetal well-being

2. Take the mothers vital signs and tell the mother that bed rest is required to conserve oxygen.

3. Notify the physician of the findings. 4. Reposition the mother and check the

monitor for changes in the fetal tracing

Answer is 1

• Accelerations are transient increases in the fetal heart rate that often accompany contractions or are caused by fetal movement.

• Episodic accelerations are thought to be a sign of fetal-well being and adequate oxygen reserve.

A nurse is admitting a pregnant client to the labor room and attaches an external electronic fetal monitor to the client’s abdomen. After attachment of the monitor, the initial nursing assessment is which of the

following? 1. Identifying the types of accelerations 2. Assessing the baseline fetal heart rate 3. Determining the frequency of the

contractions 4. Determining the intensity of the

contractions

Answer is 2

• Assessing the baseline fetal heart rate is important so that abnormal variations of the baseline rate will be identified if they occur.

• Options 1 and 3 are important to assess, but not as the first priority.

A nurse is monitoring a client in labor. The nurse suspects umbilical cord compression if which of the following is noted on the external

monitor tracing during a contraction?

1. Early decelerations

2. Variable decelerations

3. Late decelerations

4. Short-term variability

Answer is 2

• Variable decelerations occur if the umbilical cord becomes compressed, thus reducing blood flow between the placenta and the fetus.

• Early decelerations result from pressure on the fetal head during a contraction.

• Late decelerations are an suggests utero-placental insufficiency during a contraction.

• Short-term variability refers to the beat-to-beat range in the fetal heart rate.

The physician asks the nurse the frequency of a laboring client’s contractions. The nurse assesses the client’s contractions by timing

from the beginning of one contraction:

1. Until the time it is completely over

2. To the end of a second contraction

3. To the beginning of the next contraction

4. Until the time that the uterus becomes very firm

Answer is 3

• This is the way to determine the frequency of the contractions

When monitoring the FHR of a client in labor, the nurse identifies an elevation of 15 beats above the baseline rate of 135 beats per minute lasting for 15 seconds. This should be

documented as:

1. An acceleration

2. An early elevation

3. A sonographic motion

4. A tachycardic heart rate

Answer is 1

• An acceleration is an abrupt elevation above the baseline of 15 beats per minute for 15 seconds; if the acceleration persists for more than 10 minutes it is considered a change in baseline rate.

• A tachycardic FHR is above 160 beats per minute.

Which of the following findings meets the criteria of a reassuring FHR

pattern?

1. FHR does not change as a result of fetal activity

2. Average baseline rate ranges between 100 - 140 BPM

3. Mild late deceleration patterns occur with some contractions

4. Variability averages between 6 - 10 BPM

Answer is 4

• Variability indicates a well oxygenated fetus with a functioning autonomic nervous system.

• FHR should accelerate with fetal movement. • Baseline range for the FHR is 120 to 160 beats

per minute. • Late deceleration patterns are never

reassuring, though early and mild variable decelerations are expected, reassuring findings.

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References

• AWHONN Clinical Position Statement

• P. Burroughs, MSN, RN

• Martin, E.J., (2002) Intrapartum Management Modules: A Perinatal Education Program. (pp 119-123). Lippincott Williams & Wilkins 3rd Edition.

• Simpson, I., & Creehan, P. (2001) Perinatal Nursing 2nd Edition, (pp 379-383). Philadelphia, New York, Baltimore, Lippincott.