Fetal heart tone (FHT) monitoring helps assess how a baby is tolerating labor. It provides information about oxygenation and overall fetal status.

There are two main ways to monitor fetal heart tones:

Methods of Fetal Heart Monitoring

1. Internal Monitoring

• A spiral electrode is inserted through the cervix and attached to the baby’s scalp
• Advantages: Very accurate and reliable
• Disadvantages: Invasive to both mother and baby

2. External Monitoring

• An ultrasound transducer is placed on the mother’s abdomen
• Advantages: Noninvasive
• Disadvantages: Less reliable than internal monitoring and may be affected by fetal position

Quiz & Video on Fetal Heart Tone Decelerations

After you read this article, be sure to take a Fetal Heart Tone Quiz and test your knowledge on this material.

How to Read the Fetal Monitoring Strip

When looking at the monitor, you will typically see:

Top Strip: Fetal Heart Rate (FHR)

• Displays the baby’s heart rate
• A squiggly line shows how the heart rate is trending
• Numbers on the side indicate heart rate ranges
• Normal baseline FHR: 110–160 beats per minute (bpm)

Bottom Strip: Uterine Contractions

This line shows the mother’s contractions and allows you to assess:

• Frequency
• Intensity
• Duration

Parts of a Contraction

• Increment: Contraction building up
• Acme: Peak of the contraction
• Decrement: Contraction decreasing
• Relaxation: Resting phase between contractions

Types of Fetal Heart Rate Patterns

Accelerations: Temporary increase in fetal heart rate

For a term fetus:

• Increase of ≥15 bpm above baseline
• Lasts at least 15 seconds
• Lasts less than 2 minutes

Causes:

• Fetal movement
• Contractions

What it Means?

• Baby is well-oxygenated
• Healthy neurologic response

Nurse’s Role:

• No intervention needed
• Continue monitoring and document

Early Decelerations

Key Concept: They mirror contractions

• Fetal heart rate dips when contraction starts
• Returns to baseline by the end of the contraction
• Heart rate remains within normal range (110–160 bpm)

Cause:

Head compression

• Contraction compresses fetal head
• Vagus nerve stimulation temporarily lowers heart rate
• Resolves as contraction ends

What It Means?

• Normal finding
• Common in active labor

Nurse’s Role:

• No intervention needed
• Continue monitoring and document

Variable Decelerations

Key Concept: Abrupt drops that look like a “V.”

• Sudden sharp drop in FHR
• May fall below 110 bpm
• Creates a V- or U-shaped pattern
• Can occur with or without contractions

Cause

Umbilical cord compression

• Cord = baby’s lifeline
• Compression decreases oxygen
• Causes sudden heart rate drop

What It Means?

• Not reassuring
• Requires intervention

Nurse’s Role:

• Change maternal position
  • Side-lying, knee-to-chest, or Trendelenburg
• Administer oxygen (follow facility protocol)
  • For fetal heart rate decelerations, recent evidence shows that routine high-flow oxygen is no longer recommended unless the mother is hypoxic. First-line interventions remain maternal repositioning, IV fluids, and stopping uterotonics.
• Stop Pitocin (if infusing)
• Perform vaginal exam: assess for cord prolapse
• Notify provider immediately

Late Decelerations

Key Concept: Occur after the peak of the contraction

• Heart rate drops after the contraction’s acme
• Does not recover until well after the contraction ends

Cause:

Uteroplacental insufficiency

• Placenta is not delivering adequate oxygen
• Indicates impaired fetal oxygenation

What It Means?

• Serious
• Requires immediate intervention

Nurse’s Role:

• Change maternal position to left lateral
• Administer oxygen (per facility protocol)
  • For fetal heart rate decelerations, recent evidence shows that routine high-flow oxygen is no longer recommended unless the mother is hypoxic. First-line interventions remain maternal repositioning, IV fluids, and stopping uterotonics.
• Stop Pitocin
• Increase IV fluids (to improve placental perfusion)
• Notify provider immediately
  • May require emergency C-section

You may be interested in Fetal Heart Monitoring Quiz

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_References:

_{American College of Obstetricians and Gynecologists. (2025). ACOG clinical practice guideline No. 10: Intrapartum fetal heart rate monitoring: Interpretation and management. Obstetrics & Gynecology, 146(4), 583–599. https://doi.org/10.1097/AOG.0000000000006049}