Peri-Facts FHR Flashcards

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.

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.