Model Answer
0 min readIntroduction
Trial of labour (TOL) refers to allowing a woman with a prior Cesarean section to attempt a vaginal delivery. The increasing rates of Cesarean sections globally, coupled with a desire to reduce maternal morbidity associated with repeat Cesarean deliveries, have led to a renewed focus on VBAC. While VBAC offers potential benefits like shorter recovery time and avoidance of surgical risks, it also carries risks like uterine rupture. Successful TOL requires careful patient selection, meticulous monitoring during labour, and a readily available infrastructure for emergency Cesarean section. The American College of Obstetricians and Gynecologists (ACOG) provides guidelines for managing TOL, which are frequently updated based on evolving evidence.
What is Trial of Labour?
Trial of labour (TOL) is the attempt to achieve vaginal delivery in a woman who has previously undergone a Cesarean section. It is not mandatory, and the decision to attempt TOL is made jointly between the patient and the obstetrician, considering the individual’s risk factors and preferences. The primary goal is to achieve a vaginal birth, avoiding the risks associated with repeat Cesarean delivery.
Indications for Trial of Labour
- Prior single low transverse Cesarean section.
- No other contraindications to vaginal delivery.
- Adequate pelvic capacity.
- Estimated fetal weight less than 4000 grams.
- Favorable cervical factors (Bishop score ≥ 6 is generally preferred).
- Availability of adequate resources for emergency Cesarean section.
Contraindications for Trial of Labour
- Prior classical or T-shaped uterine incision.
- Prior uterine rupture.
- Multiple Cesarean deliveries (generally >2).
- Unknown type of prior uterine incision.
- Certain maternal medical conditions (e.g., severe preeclampsia, placenta previa).
- Fetal malpresentation (e.g., breech).
- Fetal distress.
- Estimated fetal weight >4000 grams (macrosomia).
Managing Trial of Labour in a Patient with a Previous Cesarean Section
1. Pre-Labour Assessment & Counselling:
A thorough assessment is crucial. This includes:
- Detailed history of previous Cesarean section – incision type, indication, complications.
- Assessment of pelvic capacity.
- Estimation of fetal weight.
- Cervical assessment (Bishop score).
- Comprehensive counselling regarding the risks and benefits of TOL/VBAC versus elective repeat Cesarean section. The risk of uterine rupture is approximately 0.5-1% with TOL/VBAC.
2. Labour Management:
Continuous fetal heart rate monitoring is mandatory throughout labour. Labour should be managed actively, with early amniotomy if indicated. Epidural analgesia is permitted and often encouraged, as it doesn’t significantly increase the risk of Cesarean section. However, close monitoring is essential as epidural can sometimes mask early signs of fetal distress.
Labour Progression: A clear protocol for labour progression is essential. A prolonged first stage of labour or slow cervical dilation may necessitate Cesarean section. ACOG recommends avoiding prolonged labour and considering Cesarean section if there is no progress after a certain duration (e.g., 6-8 hours in active labour).
3. Monitoring & Emergency Preparedness:
- Continuous fetal heart rate monitoring to detect fetal distress.
- Maternal vital signs monitoring.
- Availability of immediate access to operating room and anesthesia services.
- Blood products should be readily available in case of uterine rupture and hemorrhage.
- A multidisciplinary team approach involving obstetricians, anesthesiologists, and nurses is vital.
4. Indications for Emergency Cesarean Section during TOL:
- Fetal distress (non-reassuring fetal heart rate pattern).
- Failure to progress in labour despite adequate contractions.
- Uterine rupture (abdominal pain, vaginal bleeding, fetal bradycardia).
- Maternal exhaustion or request for Cesarean section.
- Placental abruption.
5. Postpartum Care:
Close postpartum monitoring is essential, particularly for signs of hemorrhage or uterine atony. Patients should be informed about the signs and symptoms of uterine rupture even after delivery.
VBAC Rate & Factors Influencing Success
The VBAC success rate varies depending on patient selection and hospital protocols. Generally, it ranges from 60-80% in appropriately selected patients. Factors associated with higher success rates include:
- Prior vaginal delivery.
- Favorable Bishop score.
- Low transverse uterine incision.
- Single gestation.
- Normal body mass index (BMI).
Conclusion
Trial of labour after Cesarean section is a viable option for appropriately selected patients, offering the potential benefits of vaginal delivery. However, it requires meticulous patient assessment, careful labour management, and a robust system for emergency Cesarean section. Shared decision-making between the patient and obstetrician, based on a thorough understanding of the risks and benefits, is paramount. Continuous monitoring and preparedness for complications are crucial for ensuring a safe outcome for both mother and baby.
Answer Length
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