Study Notes on Fetal Assessment During Labor

FETAL ASSESSMENT DURING LABOR

Introduction

• Focus on the importance of fetal monitoring during labor to ensure fetal well-being.

WHY FETAL MONITORING?

• Fetal response is critical during labor.

• Ensuring adequate oxygen supply is essential to prevent fetal compromise.

• Causes of decreased oxygen supply include:

  • Reduction of blood flow through maternal vessels:

  • Hypertension

  • Hypotension

  • Hypovolemia

  • Reduction in oxygen content in maternal blood:

  • Anemia

  • Alterations in fetal circulation:

  • Compression of the umbilical cord

BASIS FOR MONITORING

• Uterine activity: Monitoring provides essential information on uterine contractions.

• Fetal compromise:

  • Goals of intrapartum fetal heart rate (FHR) monitoring:

  • Identify normal (reassuring) patterns.

  • Differentiate from abnormal (non-reassuring) patterns indicative of fetal compromise.

NORMAL UTERINE ACTIVITY

• Frequency of contractions: Interval from the beginning of one contraction to the beginning of the next.

• Duration: Length of each contraction.

• Strength: Assessed through palpation.

• Montevideo units: Measurement unit for uterine contractions.

• Resting tone: Evaluated through abdominal palpation between contractions.

MONITORING TECHNIQUES

Intermittent Auscultation

• Listening to fetal heart sounds at periodic intervals to assess FHR.

• Equipment: EFM (Electronic Fetal Monitor) or Doppler.

• Advantages:

  • Easy to use

  • Inexpensive

  • Less invasive than EFM

• Disadvantages:

  • Challenging on obese women

  • Does not provide a permanent record

  • Uterine activity must still be palpated.

Electronic Fetal Monitoring (EFM)

• External Monitoring:

  • Noninvasive method using ultrasound transducer and gel.

  • Uses high-frequency sound waves to monitor FHR.

  • Recorded on EMR (Electronic Medical Record) and printed on a specially formatted paper.

  • Toco transducer (tocodynamometer):

  • Monitors frequency and duration of contractions (not intensity).

  • Sensitive to pressure.

  • Bluetooth monitoring:

  • Example: Monica

  • More suitable for obese patients.

Internal Monitoring

• Required membranes must be ruptured.

• Challenges arise due to maternal size impeding accurate external readings.

• Intrauterine Pressure Catheter (IUPC):

  • A catheter placed inside the uterus to monitor pressure.

NURSING INTERVENTIONS

• Assess FHT (Fetal Heart Tone) and uterine contractions:

  • Every 15-30 minutes in the first stage of labor.

  • Every 5 minutes in the second stage of labor.

FETAL MONITOR INTERPRETATION

• Practice focusing on FHR baseline and uterine contractions:

  • Data includes multiple readings and intervals, ensuring understanding of patterns in FHR.

MONITORING TECHNIQUES (CONT’D)

Internal Fetal Monitoring

• Fetal Scalp Electrode (FSE):

  • Small spiral electrode placed on the presenting part (usually the scalp).

  • Provides accurate measurement of FHR.

FETAL HEART RATE PATTERNS

Baseline Fetal Heart Rate

• Normal range: 110-160 bpm

  • Calculated as the average rate during a 10-minute segment excluding periodic or episodic changes and segments that differ by more than 25 beats/min.

  • Requires at least 2 minutes of interpretable data for valid assessment.

Variability in FHR Patterns

• Defined as irregular waves or fluctuations in baseline FHR.

• Categories of Variability:

  • Absent: Undetectable amplitude range.

  • Minimal: Detectable amplitude range of ≤5 bpm (not always detrimental; consider fetal sleep).

  • Moderate: Amplitude range of 6-25 bpm.

  • Marked: Amplitude range of ≥25 bpm.

Sinusoidal Pattern

• Characterized by a smooth, wave-like undulation; not classified within variability categories.

• Indicates potential severe fetal anemia, chorioamnionitis, fetal sepsis, or maternal narcotic administration.

Fetal Tachycardia and Bradycardia

• Tachycardia: Defined as a heart rate greater than 160 beats/min for 10 minutes or more;

  • Causes may include early hypoxemia, maternal fever, infection, anemia, and drug use.

• Bradycardia: Heart rate less than 110 beats/min sustained for 10 minutes or more;

  • Causes may include heart block, fetal heart failure, viral infections, and structural defects.

Changes in FHR

• Periodic changes are evaluated in relation to uterine contractions (UCs):

  • Episodic (Nonperiodic) Changes: Not associated with contractions.

  • Accelerations: FHR increases by at least 15 bpm for at least 15 seconds, indicating fetal well-being triggered by movement or contractions.

Decelerations

• Types of decelerations include:

  • Early Decelerations:

  • Gradual decrease in FHR associated with fetal head compression; onset of deceleration occurs at the beginning of contractions; recovery occurs at the end of contractions.

  • Late Decelerations:

  • Gradual decrease and recovery, with nadir (lowest point) occurring after the peak of contractions; indicate uteroplacental insufficiency.

  • Variable Decelerations:

  • Abrupt decreases of at least 15 beats from baseline for at least 15 seconds; can occur any time during contractions and present in shapes such as U, V, or W; can cause brief accelerations.

  • Prolonged Decelerations:

  • A sustained decrease of at least 15 beats lasting longer than 2 minutes but less than 10 minutes.

FHR MONITORING: CARE MANAGEMENT

EFM Pattern Recognition and Interpretation

• NICHD Workshop 2008 established a three-tier system for EFM interpretation:

  • Category I: Normal patterns.

  • Category II: Indeterminate patterns.

  • Category III: Abnormal patterns.

Abnormal FHR Patterns - Nursing Management

• Essential components of FHR tracing that must be evaluated regularly include:

  • Baseline rate

  • Baseline variability

  • Presence of accelerations

  • Presence of decelerations

  • Trends over time.

• Corrective measures for abnormal components include:

  • Intrauterine resuscitation techniques:

  • Change maternal position.

  • Increase intravenous fluids.

  • Administer supplemental oxygen (10L suggested, though this practice may vary).

Other Assessment Methods and Interventions

• Additional methods include:

  • Fetal scalp stimulation.

  • Vibroacoustic stimulation.

  • Fetal scalp blood sampling.

  • Amnioinfusion.

  • Tocolytic therapy.

  • Umbilical cord acid-base determination.

PRACTICE QUESTIONS

• Example situation: While monitoring a woman in active labor, if decelerations in FHR appear at the onset of contractions and return to baseline as contractions resolve, the appropriate response includes:

  • Change the woman’s position.

  • Document findings in her record.