- Pathophysiology/Etiology
- Perineal lacerations are tears of the perineum, vagina, or cervix that happen spontaneously during vaginal childbirth as the fetal head distends the tissues. They are very common, with up to 9 in 10 first-time mothers experiencing some degree of tearing.
- Classification (Degrees of Tearing)
- 1st Degree: Involves only the perineal skin and/or vaginal mucosa.
- 2nd Degree: Extends into the fascia and muscles of the perineal body, but the anal sphincter remains intact. This is the most common type of tear requiring stitches.
- 3rd Degree: The tear extends through the perineal muscles and involves the anal sphincter complex. It is further subdivided:
- 3a: <50% of external anal sphincter (EAS) torn.
- 3b: >50% of EAS torn.
- 3c: Both EAS and internal anal sphincter (IAS) are torn.
- 4th Degree: The tear extends through the entire anal sphincter complex (EAS and IAS) and into the rectal mucosa.
- Key Risk Factors
- Nulliparity (first vaginal delivery).
- Operative vaginal delivery (forceps or vacuum).
- Midline episiotomy is associated with a higher risk of severe (3rd/4th degree) tears.
- Macrosomia (increased fetal weight).
- Fetal malpresentation (e.g., persistent occiput posterior position).
- Advancing gestational age.
- Diagnosis
- Dx is made by a thorough, systematic visual and digital examination of the vagina, perineum, and rectum immediately after delivery. A digital rectal exam is crucial to assess the integrity of the anal sphincter and rectal mucosa.
- Management/Treatment
- 1st Degree: May not require sutures if edges are well-approximated and not bleeding.
- 2nd Degree: Requires surgical repair, typically by suturing the muscle and mucosal layers. A continuous suture technique is preferred over interrupted sutures to reduce postpartum pain.
- 3rd & 4th Degree (OASIS - Obstetric Anal Sphincter Injuries): Require meticulous surgical repair in an operating theatre with adequate anesthesia (e.g., epidural or spinal).
- The rectal mucosa (in 4th-degree tears) is repaired first, followed by the internal and external anal sphincters, and then the remainder of the perineum.
- Post-Repair Care:
- Pain control: NSAIDs, acetaminophen, perineal cold packs, and sitz baths are recommended. Opiates should be avoided due to constipation risk.
- Bowel regimen: Stool softeners and laxatives are crucial for at least 6 weeks postpartum to prevent straining and wound dehiscence.
- Antibiotics: Prophylactic broad-spectrum antibiotics are recommended after OASIS repair to reduce infection risk.
- Complications & Key Associations
- Short-term: Postpartum hemorrhage, pain, infection, and wound breakdown.
- Long-term: Fecal or flatal incontinence (especially with 3rd/4th degree tears), dyspareunia (painful intercourse), rectovaginal fistula formation, and pelvic floor dysfunction.
- Women with a history of an OASIS are at higher risk for recurrence in subsequent vaginal deliveries.