Questions and Answers
What is the normal FHR range?
Baseline FHR bradycardia is defined as a baseline FHR below 160 bpm for at least 10 minutes.
True
What are some maternal causes of baseline FHR tachycardia?
Fever/infection, dehydration, hyperthyroidism, anemia, anxiety, smoking, medication response, adrenaline.
What reflects the status of the CNS in FHR variability?
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Absent FHR variability is defined as an amplitude range that is ______.
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What is considered moderate baseline FHR variability?
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What does an acceleration in FHR indicate?
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Changes in FHR can be periodic or episodic.
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What is considered a normal response of a healthy fetus during labor?
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Gray area in FHR indicates a ______ decrease that lasts for at least 30 seconds.
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Intermittent decelerations occur with more than 50% of uterine contractions.
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Study Notes
Baseline FHR
- Normal fetal heart rate (FHR) ranges from 110-160 bpm.
- Baseline determined by mean FHR over a 10-minute period, excluding accelerations or decelerations.
- At least 2 minutes of identifiable baseline segments required for determination; otherwise, it is indeterminate.
Baseline FHR Bradycardia
- Bradycardia is identified when baseline FHR is below 110 bpm for at least 10 minutes.
- Indicates increased sympathetic nervous system (SNS) tone or decreased parasympathetic nervous system (PNS) tone.
- Requires close monitoring and evaluation.
Causes of Baseline FHR Tachycardia
- Maternal factors: fever, infection, dehydration, hyperthyroidism, anemia, anxiety, smoking, certain medications, and adrenaline.
- Fetal factors: prolonged activity, chronic hypoxemia, chorioamnionitis, cardiac issues, and compensatory responses to transient hypoxemia.
Baseline FHR Variability
- Variability indicates fluctuations in baseline FHR, measured over a 10-minute interval.
- Reflects central nervous system (CNS) status.
- Evaluated using peak-to-trough amplitude while excluding sinusoidal patterns.
FHR Variability Classifications
- Absent: undetectable amplitude range.
- Minimal: detectable but ≤ 5 bpm amplitude range.
- Moderate (reassuring): amplitude range of 6-25 bpm.
- Marked: amplitude range exceeding 25 bpm.
Causes of Minimal Baseline FHR Variability
- Maternal influences: CNS depressants, alcohol, several specific pain medications, and opioids.
- Fetal influences: sleep cycles, CNS anomalies, hypoxia, cardiac defects, and vagal stimulation.
Moderate Baseline FHR Variability
- Indicates good CNS control over the FHR and sufficient oxygenation levels to the fetus.
Accelerations
- Defined as an abrupt increase in FHR, occurring within 30 seconds, with a peak of at least 15 bpm lasting for 15 seconds or more.
- Before 32 weeks gestation, accelerations are defined as a peak of at least 10 bpm lasting 10 seconds or more.
Causes of FHR Changes
- Periodic or episodic changes can result from decreased oxygenation, umbilical cord compression, and uterine contraction pressure on the fetal head.
- Healthy fetuses alternate between quiet and active sleep, impacting FHR variability.
Components of a Normal FHR Tracing
- Baseline must remain within 110-160 bpm.
- Moderate variability is reassuring.
- Presence of accelerations is a positive sign.
- Absence of decelerations is also reassuring.
- Uterine contraction patterns must be monitored.
5 Steps to Interpreting FHR Tracing
- Measure baseline FHR over a 10-minute window.
- Assess variability and categorize it as absent, minimal, moderate, or marked.
- Analyze the presence of accelerations, reassuring with active fetal movement.
- Note the absence of decelerations as a positive indicator.
- Review uterine contraction patterns in relation to FHR changes.
Periodic FHR Pattern
- FHR patterns that are directly linked to uterine contractions.
Episodic FHR Pattern
- FHR patterns that occur independently from uterine contractions.
Deceleration
- Characterized by a decrease in FHR of at least 15 bpm, lasting at least half of the uterine contractions observed in any 20-minute segment.
Intermittent Decelerations
- Occur with less than 50% of uterine contractions within a 20-minute timeframe.
Gradual FHR Decrease
- Defined by a reduction from the onset to the nadir (lowest point) of FHR, taking longer than 30 seconds.
Early Decelerations
- Normal fetal response to labor as pressure from the cervix is transmitted to the fetal head during contractions.
- Occurs concurrently with uterine contractions and requires a normal FHR baseline with moderate variability.
- Gradual decrease and return of FHR, typically reflecting contraction timing.
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Description
Test your knowledge of fetal heart rate (FHR) terminology and definitions with these flashcards. This quiz covers key concepts like baseline FHR and bradycardia, providing a solid foundation for understanding FHR patterns. Ideal for nursing and midwifery students.
