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Am Fam Physician. 2021;103(12):745-752

Published online: April 19, 2021.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Obstetric lacerations are a common complication of vaginal delivery. Lacerations can lead to chronic pain and urinary and fecal incontinence. Perineal lacerations are defined by the depth of musculature involved, with fourth-degree lacerations disrupting the anal sphincter and the underlying rectal mucosa and first-degree lacerations having no perineal muscle involvement. Late third-trimester perineal massage can reduce lacerations in primiparous women; perineal support and massage and warm compresses during the second stage of labor can reduce anal sphincter injury. Conservative care of minor hemostatic first- and second-degree lacerations without anatomic distortion reduces pain, analgesia use, and dyspareunia. Minor hemostatic lesions with anatomic disruption can be repaired with surgical glue. Second-degree lacerations are best repaired with a single continuous suture. Lacerations involving the anal sphincter complex require additional expertise, exposure, and lighting; transfer to an operating room should be considered. Limited evidence suggests similar results from overlapping and end-to-end external sphincter repairs. Postdelivery care should focus on controlling pain, preventing constipation, and monitoring for urinary retention. Acetaminophen and nonsteroidal anti-inflammatory drugs should be administered as needed. Opiates should be avoided to decrease risk of constipation; need for opiates suggests infection or problem with the repair. Osmotic laxative use leads to earlier bowel movements and less pain during the first bowel movement. Simulation models are recommended for surgical technique instruction and maintenance, especially for third- and fourth-degree repairs.

Perineal and vaginal lacerations are common, affecting as many as 79% of vaginal deliveries, and can cause bleeding, infection, chronic pain, sexual dysfunction, and urinary and fecal incontinence.1,2

WHAT'S NEW ON THIS TOPIC

Obstetric Lacerations

Surgical glue repairs of hemostatic first-degree lacerations are faster, require less anesthetic, and cause less pain than suture repairs with similar results at six weeks postpartum.

Approximately 3% of obstetric lacerations involve clinically evident obstetric anal sphincter injuries, which double the risk of fecal incontinence at five years postpartum.

Clinical recommendationEvidence ratingComments
Digital perineal self-massage starting at 35 weeks' gestation reduces perineal lacerations during labor in primiparous women with a number needed to treat of 15 to prevent one laceration.5 ACochrane review involving four trials with 2,497 women
Perineal massage, warm compresses, and perineal support during the second stage of labor reduce anal sphincter injury.11,12 ACochrane review with four studies involving 1,799 women for warm compresses, six studies involving 2,618 women for perineal massage, and a systematic review of manual perineal support including six randomized and nonrandomized studies involving 81,391 women
Repairing hemostatic first- and second-degree lacerations does not improve short-term outcomes compared with conservative care.2 BCochrane review involving two studies with 154 women showing similar results in both groups
During a suture repair of a first- or second-degree laceration, leaving the skin unsutured reduces pain and dyspareunia at three months postpartum.24 BRandomized controlled trial of 1,780 women with first- or second-degree lacerations
Surgical glue can repair first-degree lacerations with similar cosmetic and functional outcomes with less pain, less time, and lower local anesthetic use.22 BRandomized controlled trial of 102 patients, with 74 patients randomized to surgical glue
Continuous suturing of second-degree perineal tears reduces short-term pain and pain medication use.23 ACochrane review involving 16 studies with 8,184 women showed improvements in continuous suture group but no differences in long-term pain
Local perineal cooling during the first three days after perineal repair reduces pain.33 BCochrane review involving 10 studies with 1,825 women showed improvement in pain compared with no treatment

Grading of Lacerations

Criteria from the American College of Obstetricians and Gynecologists (ACOG) help determine repair techniques and estimate prognosis.1 Figure 1 shows the muscles affected by perineal lacerations.

FIRST- AND SECOND-DEGREE LACERATIONS

First-degree lacerations involve only the perineal skin without extending into the musculature.1 Second-degree lacerations involve the perineal muscles without affecting the anal sphincter complex.

THIRD-DEGREE LACERATIONS

Approximately 3% of lacerations involve clinically evident obstetric anal sphincter injuries, doubling the risk of fecal incontinence at five years postpartum.3,4 These lacerations are further classified by the extent of anal sphincter injury (Table 1).1

DegreeDescription
FirstLaceration of perineal skin only
SecondLaceration involving the perineal muscles but not involving the anal sphincter
ThirdLaceration involving the anal sphincter muscles
  1. Less than 50% external anal sphincter involvement

  2. More than 50% external anal sphincter involvement

  3. External and internal anal sphincter

FourthLaceration involving the anal sphincter complex and rectal epithelium

The majority of obstetric anal sphincter injuries are third-degree lacerations that involve the anal sphincter complex without disrupting the rectal mucosa.1 The anal sphincter complex comprises the larger external anal sphincter containing striated muscle and a distinct capsule plus the small internal anal sphincter of involuntary smooth muscle that often cannot be identified.

FOURTH-DEGREE LACERATIONS

Fourth-degree lacerations are the most severe, involving the rectal mucosa and the anal sphincter complex.1 Disruption of the fragile internal anal sphincter routinely leads to epithelial injury. Fourth-degree lacerations occur in less than 0.5% of patients.1 Figure 2 shows a fourth-degree perineal laceration.

Prevention of Obstetric Lacerations

BEFORE DELIVERY

A Cochrane review demonstrated that digital perineal self-massage starting at 35 weeks' gestation reduces the rate of perineal lacerations in primiparous women with a number needed to treat of 15 to prevent one laceration.5 Because the review included fewer than 2,500 patients, reductions could not be demonstrated for specific laceration grades. Women reported that self-massage was initially uncomfortable, unpleasant, and even painful, but nearly 90% would recommend the technique to others.6

DURING DELIVERY

Studies of prevention during delivery have focused on prevention of obstetric anal sphincter injuries. Most risk factors involve labor management, including labor induction, labor augmentation, use of epidural anesthesia, delivery with persistent occipitoposterior positioning, and operative vaginal deliveries7 (Table 21,8,9 ). Although epidural anesthesia increases risk of obstetric anal sphincter injuries through increased operative vaginal delivery, epidural use reduces lacerations overall.10

Fetal risk factors
Large fetal weight (> 4,000 g [8 lb, 13.1 oz])
Occipitotransverse or occipitoposterior position at delivery
Intrapartum risk factors
Delivery in lithotomy position
Epidural anesthesia (increases risk of severe lacerations, decreases overall lacerations)
Midline episiotomy
Operative vaginal delivery (i.e., forceps, vacuum)
Oxytocin use
Prolonged second stage of labor (> 60 minutes)
Maternal risk factors
20 years or younger
Asian ethnicity9
Nulliparity
Vaginal birth after cesarean delivery

Several labor techniques can reduce anal sphincter injuries. During the second stage of labor, perineal massage and application of a warm compress to the perineum are beneficial.11 Perineal support during delivery, variably described as squeezing the lateral perineal tissue with the first and second fingers of one hand to lower pressure in the middle posterior perineum while the other hand slows the delivery of the fetal head, reduces obstetric anal sphincter injuries, with a number needed to treat of 37 in a systematic review.12,13

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