What is the management of fetal heart rate tracings in the second stage of labor?

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From the Guidelines

The management of fetal heart rate tracings in the second stage of labor should prioritize continuous electronic fetal monitoring, with interpretation every 15-30 minutes for low-risk patients and every 5-15 minutes for high-risk patients, and prompt intervention for abnormalities, such as recurrent late decelerations, prolonged decelerations, or bradycardia, using measures like maternal repositioning, discontinuation of oxytocin, administration of oxygen, and increasing intravenous fluids, as outlined in the NICHD categories 1.

Key Principles

  • Continuous electronic fetal monitoring is essential throughout the second stage of labor to promptly identify and address any abnormalities in fetal heart rate tracings.
  • Interpretation of fetal heart rate tracings should be done regularly, with the frequency depending on the patient's risk level.
  • The NICHD categorization system (Category I: Normal, Category II: Indeterminate, Category III: Abnormal) provides a framework for interpreting fetal heart rate tracings and guiding management decisions 1.

Management of Abnormalities

  • For Category II tracings, which are indeterminate and may indicate potential fetal compromise, general measures such as discontinuing oxytocin, considering the potential need to expedite delivery if abnormalities persist or worsen, and implementing intrauterine resuscitation measures like amnioinfusion for variable decelerations or tocolysis for uterine tachysystole should be considered 1.
  • Category III tracings, which are abnormal and indicate fetal compromise, require immediate intervention, including discontinuing oxytocin and expediting delivery, potentially via operative vaginal or cesarean delivery 1.

Physiological Basis for Interventions

  • The goal of interventions is to improve uteroplacental perfusion, relieve cord compression, and ensure adequate fetal oxygenation during the second stage of labor, which is crucial for preventing fetal compromise and adverse outcomes 1.

Normal FHR Changes

  • It's essential to recognize normal changes in fetal heart rate during the second stage of labor, such as increased baseline variability and transient decelerations with pushing efforts, which typically resolve between contractions and do not require intervention 1.

From the Research

Management of Fetal Heart Rate Tracings

Overview of Fetal Heart Rate Monitoring

  • Fetal heart rate (FHR) monitoring is widely used during labor to assess fetal well-being 2.
  • The normal FHR tracing includes a baseline rate between 110-160 beats per minute (bpm), moderate variability (6-25 bpm), presence of accelerations, and no decelerations 2.
  • Abnormal FHR patterns, such as tachycardia, bradycardia, and decelerations, can indicate fetal distress or acidosis 2, 3.

Characteristics of Fetal Heart Rate Tracings During Labor

  • FHR tracings during the second stage of labor can be abnormal in up to 75% of cases, with nulliparity, cord problems, and male sex being independent factors affecting the occurrence of abnormal tracings 3.
  • Maternal heart rate (MHR) can sometimes be mistaken for FHR, leading to erroneous interpretation and management 4.
  • MHR has a lower baseline rate and more marked beat-to-beat variability compared to FHR 4.

Clinical Significance of Abnormal FHR Patterns

  • Abnormal FHR patterns during the second stage of labor are associated with higher rates of operative delivery, lower Apgar scores, and increased risk of fetal acidosis 3.
  • Late decelerations, bradycardia, and abnormal FHR patterns during the first stage of labor can jeopardize fetal well-being and may require expedited delivery 3.
  • Quantitative measures of FHR monitoring, such as deceleration and variability, can be useful in predicting fetal distress 5.

Fetal Monitoring During the Active Second Stage of Labor

  • The active second stage of labor is characterized by frequent and prolonged uterine contractions, leading to increased intrauterine pressure and reduced placental perfusion 6.
  • Fetal monitoring during this stage is crucial, with Melchior's FHR classification being specific to this stage and describing five fetal heart rate patterns 6.
  • No method of fetal monitoring has a 100% sensitivity to detect metabolic acidosis, and a close follow-up of FHR is required during this stage 6.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Research

[Fetal heart rate during labour: definitions and interpretation].

Journal de gynecologie, obstetrique et biologie de la reproduction, 2008

5
Research

Toward quantitative fetal heart rate monitoring.

IEEE transactions on bio-medical engineering, 2006

6
Research

[Fetal monitoring during the active second stage of labor].

Journal de gynecologie, obstetrique et biologie de la reproduction, 2008

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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