SUMMARY:

Lacerations during vaginal delivery are common and may involve the cervix, vagina, vulva, and perineum. While most of these lacerations do not result in poor long-term outcomes, perineal lacerations that involve the anal sphincter complex may be associated with a higher risk of pelvic floor injury, urinary and fecal incontinence, pain, and sexual dysfunction. While some risk factors are not modifiable, other risk factors are associated with practices at the time of delivery, including episiotomy, perineal protection during delivery, and surgical repair technique

Background

• Research and data collection on obstetric lacerations can be challenging given variations in classification and difficulty separating independent risk factors
• Approximately 53% to 79% of patients have lacerations during vaginal delivery
  • Estimated 3.3% third-degree perineal lacerations and 1.1% fourth-degree perineal lacerations
  • Together termed Obstetric Anal Sphincter Injury (OASIS)
• Patients with OASIS and/or episiotomies during delivery are more likely to have anal incontinence later in life
• Risk factors for OASIS include
  • Operative deliveries, such as forceps, vacuum
  • Midline episiotomy
  • Increased fetal birth weight
  • History of previous OASIS

Perineal Lacerations Based on the Degree of Injury

• First degree: Injury to perineal skin only
• Second degree: Involving perineal muscles without injury to the anal sphincter
• Third degree: Injury involving anal sphincter complex, divided by depth of injury
  • 3a | Injury of less than 50% of external anal sphincter
  • 3b | Injury of more than 50% of external anal sphincter
  • 3c | Full thickness injury to the external anal sphincter and involvement of the internal sphincter
• Fourth degree: Injury to all of the above plus the anal epithelium

Prevention Strategies

• Reduces risk
  • Perineal massage at term and/or during second stage of labor
  • warm compresses during second stage
• Possibly reduces risk
  • manual perineal support during delivery
  • lateral birthing position
• Does not appear to reduce risk
  • Delayed pushing

Note: There have been many studies to evaluate how to prevent severe lacerations at delivery, with varying quality of evidence

Role of Episiotomy

• Episiotomy is intentional enlargement of posterior aspect of vagina or perineum, either midline (median) or mediolateral
  • Midline (median) episiotomy: Within 3mm of the midline and extends zero to twenty-five degrees of the sagittal plan
  • Mediolateral: Also within 3mm of the midline and extends laterally towards the ischial tuberosity at an angle of at least sixty degrees
• Existing evidence supports restrictive episiotomy vs routine
• Some evidence that mediolateral episiotomy is superior to midline episiotomy, if necessary, with lower rates of OASIS but may be associated with higher rates of perineal pain and dyspareunia

Management

• First-degree perineal lacerations and non-perineal lacerations
  • Repair only if bleeding or distorting anatomy
• Second-degree perineal lacerations
  • Repair with absorbable synthetic suture with continuous suturing
• Occult OASIS
  • Defined as OASIS not identified at time of delivery or no clinical findings but recognized later by endoanal ultrasonography
  • Can occur in up to 27% of women after their first vaginal delivery
  • Clinical training and experience can improve detection rates
  • Consider digital rectal exam at time of delivery to identify occult OASIS | Identification of OASIS improved with digital rectal exam and examination by an experienced provider
• Repair of OASIS guided by expert opinion
  • Repair in layers: First anal mucosa, then internal anal sphincter (if identifiable), followed by external anal sphincter
  • End-to-end vs overlap repair of anal sphincter
    • Both acceptable
    • Overlap repair associated with lower rates of fecal incontinence
• Use of antibiotics
  • Large UK-based multi-center double-blinded RCT demonstrated that a single dose of second-generation cephalosporin decreased infection risk immediately and at 6 weeks postpartum following operative vaginal birth (see Anode Trial summary below in ‘Related ObG Entries’)
  • Dose used in trial: Single dose IV 1 g amoxicillin and 200 mg clavulanic acid administered as soon as possible and no more than 6 h after giving birth

ACOG states that…

…use of routine prophylactic antibiotics before delivery would not be recommended. Because wound infections and complications are more common in the setting of a third- or fourth-degree laceration, it may be more judicious to consider antibiotics if a third- or fourth-degree laceration occurs

Follow-up Care

• Postpartum
  • Avoid constipation postpartum, consider oral laxatives
  • Improve pain control but beware constipating effect of opiates
  • Closely monitor spontaneously voiding for signs of urinary retention and discomfort from bladder distention
• Short-term close follow up for OASIS recommended
  • 25% of patients have wound breakdown
  • 20% have infection
• Pelvic physical therapy does not appear to alter long-term anal incontinence risk
• Patients with OASIS complications and/or psychological trauma after OASIS may be offered primary C-section for subsequent deliveries

KEY POINTS:

• Most women will have a first- or second-degree laceration
• Obstetric anal sphincter injuries are comprised of third-degree and fourth-degree perineal lacerations with higher risk of anal incontinence later in life
• Lacerations that are not bleeding or do not distort anatomy do not require repair
• Episiotomies should not be routinely utilized | Reserved for situations based on clinical judgement

Learn More – Primary Sources 

ACOG PB 198: Prevention and Management of Obstetric Lacerations at Vaginal Birth

ACOG PB 199: Use of Prophylactic Antibiotics in Labor and Delivery

ACOG CO 766: Approaches to Limit Intervention During Labor and Birth

Related ObG Topics:

ACOG Responds to ANODE Trial and Antibiotic Use for Operative Vaginal Delivery

Forceps/Vacuum Delivery vs Cesarean Section and Adverse Maternal and Perinatal Outcomes

Operative Vaginal Birth: Indications and Clinical Considerations

ANODE RCT Results: Antibiotic Prophylaxis for Forceps or Vacuum Extraction?