6.2 Perineal Trauma Assessment, Classification (1st to 4th Degree) & Care Principles

Perineal Trauma Assessment, Classification (1st to 4th Degree) & Care Principles

Perineal trauma affects approximately 85% of women undergoing vaginal birth in the United Kingdom, occurring either spontaneously or through surgical incision (episiotomy). Inaccurate assessment or suboptimal surgical repair can lead to debilitating long-term physical and psychological morbidity, including persistent perineal pain, superficial and deep dyspareunia, wound breakdown, urinary dysfunction, and anal incontinence. Registered midwives must possess comprehensive competence in systematic anatomical assessment, precise classification under the Royal College of Obstetricians and Gynaecologists (RCOG) Green-top Guideline No. 29, evidence-based repair techniques, and post-injury management bundles.

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Systematic Genital Tract Assessment Protocol

Following birth, every woman who has sustained visible trauma or reports perineal discomfort must be offered a systematic assessment of the genital tract. Clinical assessment must be conducted with extreme sensitivity, privacy, and full informed consent.

┌─────────────────────────────────────────────────────────────────────────────────┐
│               GENITAL TRACT SYSTEMATIC ASSESSMENT SEQUENCE                      │
└─────────────────────────────────────────────────────────────────────────────────┘
                                         │
         ┌───────────────────────────────┼───────────────────────────────┐
         ▼                               ▼                               ▼
┌─────────────────┐             ┌─────────────────┐             ┌─────────────────┐
│ 1. Preparation  │             │ 2. Visualisation│             │ 3. Digital Exam │
├─────────────────┤             ├─────────────────┤             ├─────────────────┤
│• Informed consent│             │• Part vulva with│             │• Insert index   │
│• Lighting & bed │             │  sterile swabs  │             │  finger in anal │
│• Inhaled / local│             │• Inspect cervix,│             │  canal          │
│  analgesia      │             │  vaginal walls, │             │• Palpate EAS/IAS│
│• Sterile gloves │             │  perineal body  │             │  between thumb &│
│  & drapes       │             │• Identify apex  │             │  finger         │
└─────────────────┘             └─────────────────┘             └─────────────────┘

Practical Assessment Steps

1. Environment & Analgesia: Ensure optimal lighting using an adjustable examination lamp. Position the woman comfortably in the lithotomy position (with leg supports or lithotomy poles) or lateral position. Provide effective analgesia—inhaled nitrous oxide/oxygen (Entonox) combined with local infiltration of 1% lidocaine hydrochloride (up to a maximum dose of 3 mg/kg or 20 mL of 1% solution) before touching tender wound edges.
2. Visual Inspection: Gently part the labia and cleanse the perineum with warm sterile saline. Systematically inspect the structures from superior to inferior: clitoral hood and labia minora, urethra, bilateral vaginal lateral walls, posterior vaginal wall, cervix (if high-volume bleeding or instrumental delivery occurred), and the perineal body.
3. Locating the Wound Apex: Part the vaginal walls using sterile gauze swabs to identify the highest point (apex) of any vaginal laceration, ensuring that occult high vaginal vault tears are not overlooked.
4. Mandatory Digital Rectal Examination (DRE): Prior to suturing any perineal laceration or episiotomy, the clinician must perform a routine digital rectal examination. The practitioner inserts a gloved index finger into the anal canal while simultaneously palpating the perineal body between the index finger and thumb ("pill-rolling" technique). The patient is asked to contract the pelvic floor if conscious, assessing the continuous circular muscular resistance of the external anal sphincter (EAS) and internal anal sphincter (IAS) and confirming that the rectal mucosa is completely intact.

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RCOG Classification of Perineal Tears (Green-top Guideline No. 29)

The RCOG standardises the anatomical classification of perineal trauma into four distinct degrees. Precise anatomical classification is clinically vital because it dictates the surgical environment, the required skill level of the operating clinician, the suture materials used, and the subsequent postnatal follow-up pathway.

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Surgical Repair Principles & Suture Techniques

Surgical repair of perineal trauma aims to restore normal anatomical alignment, establish haemostasis, promote rapid tissue healing, and minimize postoperative pain and dyspareunia.

┌─────────────────────────────────────────────────────────────────────────────────┐
│                     2ND DEGREE REPAIR: THREE-STAGE CONTINUOUS                   │
└─────────────────────────────────────────────────────────────────────────────────┘
       Stage 1                          Stage 2                          Stage 3
 ┌──────────────────┐             ┌──────────────────┐             ┌──────────────────┐
 │  Vaginal Mucosa  │             │ Perineal Muscle  │             │  Perineal Skin   │
 ├──────────────────┤             ├──────────────────┤             ├──────────────────┤
 │• Start 1 cm above│             │• Continuous or   │             │• Subcuticular    │
 │  vaginal apex    │  ─────────► │  interrupted     │  ─────────► │  technique       │
 │• Continuous      │             │• Re-appose deep  │             │• Buried knot at  │
 │  non-locking     │             │  transverse &    │             │  vaginal introitus│
 │• Vicryl Rapide   │             │  bulbocavernosus │             │• Zero skin knots │
 └──────────────────┘             └─────────────────┘             └──────────────────┘

Second-Degree Tear Repair Protocol

Robust Cochrane systematic review evidence confirms that second-degree perineal lacerations and episiotomies should be repaired using a continuous non-locking suture technique across all three layers:

1. Suture Material: Rapidly absorbable synthetic braided suture material, specifically polyglactin 910 (Vicryl Rapide), is the gold standard. Compared to traditional standard polyglactin (Vicryl) or chromic catgut, Vicryl Rapide loses tensile strength by 10 to 14 days and undergoes complete enzymatic absorption by 42 days, dramatically reducing the incidence of stitch pain, suture knot extrusion, and the need for suture removal.
2. Stage 1 (Vaginal Mucosa): Anchor the first suture approximately 1 cm above the apex of the vaginal laceration to secure any retracted bleeding arterioles. Advance downward to the hymenal ring using a loose, continuous non-locking stitch. Non-locking sutures are essential because locking (blanket) stitches cause localized tissue strangulation, ischaemia, and severe postoperative pain.
3. Stage 2 (Perineal Musculature): Without cutting the suture thread, bring the needle into the deep perineal space. Re-approximate the torn muscle bellies of the transverse perineal and bulbocavernosus muscles using continuous or interrupted deep bites, eliminating dead space where a haematoma could form.
4. Stage 3 (Perineal Skin): Pass the suture through the subcutaneous layer immediately beneath the dermis toward the introitus using a subcuticular technique. Conclude by tying a buried knot behind the hymenal ring. Subcuticular skin closure avoids transcutaneous skin sutures, eliminating skin nerve entrapment and superficial pain.

Third- and Fourth-Degree Tear Repair (OASIS)

Obstetric Anal Sphincter Injuries must never be repaired in a standard delivery room. The woman must be transferred promptly to an operating theatre equipped with operating lights, suction, surgical instruments, and trained scrub staff:

• Anaesthesia: Spinal or epidural regional anaesthesia (or general anaesthesia if regional is contraindicated) is mandatory to achieve profound pelvic floor muscle relaxation, allowing retracted sphincter ends to be visualised without tension.
• Rectal Mucosa Repair (4th Degree): Re-approximate the disrupted anal rectal mucosa using interrupted or continuous fine absorbable sutures (3-0 polyglactin / Vicryl), burying knots in the submucosa away from the anal lumen or tying within the lumen to prevent stitch sinus formation.
• Internal Anal Sphincter Repair (3c/4th Degree): The IAS provides 70–80% of resting anal canal tone and is crucial for passive fecal continence. Identify the pale, circular fibrous muscle band and re-approximate it separately using interrupted or horizontal mattress sutures with 3-0 PDS (polydioxanone) or 3-0 Vicryl.
• External Anal Sphincter Repair (3a/3b/3c/4th Degree): The EAS can be repaired using either an end-to-end technique (for partial tears or grade 3a) or an overlap technique (for full-thickness grade 3b/3c/4th degree tears where the severed ends have retracted). Use monofilament absorbable sutures (such as 3-0 PDS) or 2-0 Vicryl, placing mattress sutures that grasp the fibrous sphincter capsule.

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Postoperative Care Bundle for OASIS

Following surgical repair of a 3rd or 4th degree tear, an evidence-based care bundle must be initiated to prevent devastating short- and long-term sequelae:

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Long-term Recovery & Counselling for Future Delivery Mode

At the 6- to 12-week multidisciplinary review, the woman's functional recovery is thoroughly evaluated. Approximately 60–80% of women who undergo prompt, high-quality primary OASIS repair remain asymptomatic at 12 months.

Future Mode of Birth Decision-Making

Counselling regarding future pregnancies and mode of delivery must be objective, individualized, and transparent:

• Recurrence Risk: The baseline risk of sustaining a recurrent OASIS in a subsequent vaginal birth is approximately 5% to 7% (compared to a 2–3% baseline risk in the general obstetric population).
• Elective Caesarean Section: An elective caesarean section should be strongly recommended if the woman is symptomatic (reporting any degree of faecal urgency, flatus incontinence, or faecal soiling), or if objective investigations (endoanal ultrasound or anal manometry) reveal significant residual sphincter defects or abnormal squeeze pressures.
• Supported Vaginal Birth: If the woman is completely asymptomatic, has normal sphincter anatomy and squeeze pressures, and desires a vaginal birth, a subsequent vaginal birth is clinically supported. During subsequent labour, active management includes ensuring an experienced midwife or obstetrician attends the birth, avoiding unindicated instrumental deliveries, and using perineal protection techniques. RCOG GTG29 finds no evidence that prophylactic episiotomy prevents recurrent OASIS, so episiotomy is performed only when clinically indicated.