What is the reason for continuous Electronic Fetal Monitoring (EFM) during a trial of labor after Caesarean section (TOLAC)?

Continuous Electronic Fetal Monitoring During TOLAC

The primary reason for continuous electronic fetal monitoring (EFM) during a trial of labor after cesarean section (TOLAC) is to observe for fetal heart rate (FHR) changes as an indication of uterine rupture.

Rationale for Continuous EFM During TOLAC

Continuous EFM is essential during TOLAC because:

1. Detection of Uterine Rupture: Nonreassuring fetal status (NRFS) often precedes uterine rupture, which is a serious complication of TOLAC. Women requiring repeat cesarean for NRFS during TOLAC are at significantly increased risk of uterine rupture (adjusted odds ratio 3.32) compared to those requiring cesarean for other indications 1.

2. Risk Assessment: TOLAC carries a higher risk of uterine rupture compared to elective repeat cesarean delivery. The risk of uterine rupture during TOLAC is approximately 1% with oxytocin use and higher (about 2%) with vaginal prostaglandins 2.

3. Early Intervention: Continuous monitoring allows for prompt identification of FHR abnormalities that may indicate fetal compromise, enabling timely intervention to prevent adverse outcomes.

Monitoring Protocol During TOLAC

The monitoring protocol during TOLAC should include:

• Continuous electronic fetal monitoring throughout labor
• Regular assessment of the FHR tracing by physicians and labor nurses
• Documentation of any abnormalities in the FHR pattern
• Prompt communication of concerning findings to the healthcare team

Risks and Benefits of Continuous EFM

While continuous EFM is standard practice during TOLAC, it's important to understand its overall benefits and limitations:

• Benefits: Continuous EFM has been shown to reduce neonatal seizures (though the number needed to treat is high at 661) 3.

• Limitations: Continuous EFM has not been shown to reduce overall neonatal death rates or the occurrence of cerebral palsy, and it increases cesarean delivery rates overall and instrumental vaginal births 3.

Management of Abnormal FHR During TOLAC

When abnormalities are detected during continuous EFM in TOLAC:

• Assess for signs of uterine rupture (sudden onset of FHR abnormalities, loss of contractions, maternal pain)

• Consider intrauterine resuscitation measures including:

  • Changing maternal position
  • Assessing maternal vital signs
  • Discontinuing oxytocin if being used
  • Administering oxygen
  • Performing vaginal examination
  • Administering IV fluids
  • Considering amnioinfusion for variable decelerations 4

• Prepare for emergency cesarean delivery if FHR abnormalities persist or worsen

Common Pitfalls and Caveats

1. Overreliance on technology: While continuous EFM is essential during TOLAC, clinical assessment remains important. FHR changes may precede but are not always specific for uterine rupture.

2. Delayed response: Failure to promptly recognize and respond to nonreassuring FHR patterns can lead to adverse outcomes.

3. Inappropriate induction methods: The use of misoprostol for induction during TOLAC appears to significantly increase the risk of uterine rupture and is not recommended 2.

4. Prolonged labor: In the active phase of labor during TOLAC, it is recommended that the total duration of failure to progress should not exceed 3 hours, after which cesarean delivery should be performed 2.

Continuous EFM remains the standard of care for TOLAC, as it provides the best opportunity to detect early signs of uterine rupture through changes in the FHR pattern, allowing for timely intervention to prevent adverse maternal and neonatal outcomes.