Trial of Labor After Cesarean Section

Introduction

• The American College of Obstetricians and Gynecologists defines TOLAC as “a planned attempt to deliver vaginally by a woman who has had a previous cesarean delivery, regardless of outcome”.¹
  • If the attempt is successful, then the birth is called a vaginal birth after cesarean delivery (VBAC).¹
  • An estimated 60-80% of TOLACs result in VBACs.¹
• The benefits of TOLAC include avoiding major abdominal surgery, a faster recovery, and a lower risk of hemorrhage, thromboembolism, and infection.1
• Risks of TOLAC include uterine rupture (0.5-0.9%), uterine dehiscence, and requiring an emergent cesarean delivery.¹
  • The risk of uterine rupture in a patient undergoing TOLAC who has had multiple cesarean deliveries is estimated to be 0.9-3.7%.¹
• Anesthetic concerns of TOLAC are pain control during the TOLAC, failure of TOLAC, and need for urgent conversion to cesarean delivery, as well as resuscitation in the event of uterine rupture.²

Eligibility/Success Calculators

• TOLAC is generally offered to patients who have had one cesarean delivery via a low-transverse incision.¹
• TOLAC is generally not offered to patients at high risk of uterine rupture or patients who have a contraindication to vaginal delivery, e.g., abnormal placentation.¹
• Several calculators exist to predict the likelihood of VBAC, but none have been shown to influence patient outcomes positively.¹
• The Maternal-Fetal Medicine Units Network has a VBAC Calculator to predict the probability of VBAC in a patient with a history of one low transverse cesarean section now presenting with a cephalic, singleton gestation at term.³ Link

Anesthetic Considerations for TOLAC/VBAC

• Anesthesiologists and obstetricians should discuss with the patient whether the patient would accept blood products due to the risk of hemorrhage and/or disseminated intravascular coagulation (DIC) from uterine rupture.^2,3
• Placing an epidural in a patient who is undergoing TOLAC is beneficial because it can be used as the anesthetic if the patient requires an urgent cesarean section, allowing the patient to avoid the risks of general anesthesia (e.g., intubation difficulties, aspiration, neonatal exposure to anesthetics).²
• Rates of uterine rupture are similar in TOLAC patients who have an epidural (0.4%) and those who do not (0.29%).⁵
• The rate of cesarean delivery in patients undergoing TOLAC was found to be significantly lower in patients who chose to have an epidural (8.7%) than in those who did not (11.8%).⁵

Uterine Rupture Diagnosis and Management

• Uterine rupture occurs when all the uterine layers completely separate, which can lead to massive hemorrhage and fetal distress (hypoxia, demise).³
  • Uterine dehiscence is when the uterine scar separates incompletely.
• TOLAC is contraindicated if the patient has a history of uterine rupture.³
  • Instead, the patient should have a scheduled cesarean section at 36-37 weeks gestational age.

Risk Factors for Uterine Rupture During TOLAC^2,3

• Labor induction or augmentation
• Previous myomectomy with entry into the endometrial cavity and resection of a large myoma from the uterine contractile area
• Maternal age ≥ 35 years at the time of the previous cesarean section
• Shorter maternal height (≤ 160cm)
• Shorter inter-delivery interval (< 16-18 months)
• Birth weight > 4000g
• Gestational age > 40 weeks
• Previous postpartum hemorrhage during cesarean delivery
• History of recurrent miscarriage (≤ 12 weeks)
• Multiple previous cesarean deliveries
• Multiparity (> 2)

Diagnosis of Uterine Rupture³

• To date, there is no proven clinical model that can predict a patient’s risk of uterine rupture.
• Clinical signs of uterine rupture include:
  • Fetal bradycardia or heart rate decelerations (most common sign)
  • Abnormal contraction pattern
  • Acute onset abdominal pain (i.e., pain out of proportion to exam)
  • Increasing epidural dose requirements
  • Vaginal bleeding
  • Loss of fetal station
  • Palpable fetal parts on abdominal exam
  • Hemodynamic instability
  • Hematuria
• If there is concern for uterine rupture, the obstetric team can perform an ultrasound to look for sonographic signs (for example, free fluid in the abdomen, expanding hematoma over the uterine scar, extrauterine fetal parts).
• Definitive diagnosis is made intra-operatively with massive hemoperitoneum and extrauterine fetal parts in the patient’s abdomen.

Management³

• Obstetric management includes emergency cesarean delivery and then uterine repair or hysterectomy.
• The anesthesia team should be prepared to manage and resuscitate the patient in the event of massive hemorrhage or DIC and induce/convert to general anesthesia.³