Appraise means of protecting the perineum in labour, use of episiotomy, and perineal tears in the parturient

Clinical overview

The perineum is the soft-tissue bridge between vagina and anus that every vaginal birth must negotiate. Most parturients sustain some degree of perineal trauma at first vaginal birth, and a clinically important minority sustain obstetric anal sphincter injury (OASIS) with lifelong consequences for continence, sexual function and psychological wellbeing. The registrar's task is rarely a single dramatic intervention; it is a sequence of small, evidence-graded choices across the second stage — how the head is allowed to deliver, whether and where a hand is placed, whether a warm compress is applied, whether and when an episiotomy is cut, and how completely any tear is then diagnosed and repaired. Each choice shifts the probability of an intact perineum or of a third- or fourth-degree tear by a few percentage points; together they are the difference between a woman who walks out continent and one referred to a colorectal clinic.

This objective asks you to appraise — to weigh competing techniques rather than simply recite a protocol. That weighing matters acutely in the South African setting, where most births occur in midwife-led labour wards at district level, where instrumental delivery and macrosomia are common, and where the recognition and primary repair of OASIS often falls to a registrar called from another ward. The National Integrated Maternal and Perinatal Care Guideline (NDoH, 2024) frames perineal care within respectful, woman-centred intrapartum care; getting it right is both a quality marker and a medicolegal flashpoint. This chapter sits alongside Normal labour, Instrumental delivery and OASIS, and the techniques below assume you have already mastered the mechanics of the normal second stage.

Core knowledge

Anatomy of the perineum

The perineal body is a fibromuscular pyramid into which the bulbospongiosus, superficial and deep transverse perineal muscles, the external anal sphincter (EAS) and fibres of the levator ani converge. Understand the layered structure because repair recapitulates it. From the introitus outward and downward: vaginal epithelium and submucosa; the perineal muscles and the perineal body; subcutaneous tissue and perineal skin. Posterior to the perineal body lie the EAS (a circular striated voluntary muscle), the internal anal sphincter (IAS, a smooth-muscle continuation of the rectal circular muscle — pale, glistening, and the key to continence of flatus and liquid stool) and the anorectal mucosa. See Genital anatomy for the full pelvic floor.

Classification of perineal trauma

The internationally accepted (RCOG/Sultan) classification grades severity by depth:

Third- and fourth-degree tears together constitute OASIS. A "buttonhole" tear (rectal mucosa torn with an intact sphincter) is a separate entity and is easily missed. Anterior trauma to labia, urethra and clitoris is graded separately and often left unsutured if not bleeding and well-apposed. The classification and the principles of OASIS repair are anchored in RCOG Green-top Guideline No. 29; this chapter deliberately defers the detail of OASIS recognition and repair to OASIS.

Risk factors for severe trauma

Recognising the high-risk birth lets you mobilise prevention. Classically described associations include nulliparity, larger fetal weight/macrosomia (see Macrosomia), instrumental delivery (especially forceps), occipito-posterior position, prolonged second stage, shoulder dystocia, and previous OASIS. Asian ethnicity is a frequently cited risk factor in the OASIS literature. Many of these are non-modifiable on the day; what you can modify is the conduct of the delivery itself.

Assessment

Antenatal and intrapartum appraisal

Identify the woman at elevated risk during labour: the primigravida with an estimated large baby, the persistent OP position, the instrumental birth in prospect, and crucially the woman with a previous OASIS — whose mode of delivery and perineal plan should already have been discussed and documented antenatally, with counselling about recurrence risk and the option of elective caesarean for the subtotal-incontinent or symptomatic woman.

Examining the perineum after birth

Systematic post-delivery examination is the single most important step in not missing OASIS, and it is where registrars are most often found wanting in medicolegal review. Every woman after vaginal birth — including those who appear to have an intact perineum — must have a structured genital and rectal examination. Standard teaching, reflected in RCOG GTG 29, is: