A perineal tear occurs where the external vaginal opening is too narrow to accommodate the baby. This leads to the skin and tissues in that area tearing as the baby’s head passes.
Perineal tears can range from a graze, to a large tear involving the anal sphincter (third-degree) and rectal mucosa (fourth-degree).
Perineal tears are more common with:
- First births (nulliparity)
- Large babies (over 4kg)
- Shoulder dystocia
- Asian ethnicity
- Occipito-posterior position
- Instrumental deliveries
Classification
There are four degrees of perineal tear, each involving injury to tissue beyond the previous:
- First-degree – injury limited to the frenulum of the labia minora (where they meet posteriorly) and superficial skin
- Second-degree – including the perineal muscles, but not affecting the anal sphincter
- Third-degree – including the anal sphincter, but not affecting the rectal mucosa
- Fourth-degree – including the rectal mucosa
Third-degree tears can be subcategorised as:
- 3A – less than 50% of the external anal sphincter affected
- 3B – more than 50% of the external anal sphincter affected
- 3C – external and internal anal sphincter affected
Management
First-degree tears usually do not require any sutures. When a perineal tear larger than first degree occurs, the mother usually requires sutures to correct the injury. A third or fourth-degree tear is likely to need repairing in theatre.
Additional measures are taken to reduce the risk of complications:
- Broad-spectrum antibiotics to reduce the risk of infection
- Laxatives to reduce the risk of constipation and wound dehiscence
- Physiotherapy to reduce the risk and severity of incontinence
- Followup to monitor for longstanding complications
Women that are symptomatic after third or fourth-degree tears are offered an elective caesarean section in subsequent pregnancies.
Complications
Short term complications after repair include:
- Pain
- Infection
- Bleeding
- Wound dehiscence or wound breakdown
Perineal tears can lead to several lasting complications:
- Urinary incontinence
- Anal incontinence and altered bowel habit (third and fourth-degree tears)
- Fistula between the vagina and bowel (rare)
- Sexual dysfunction and dyspareunia (painful sex)
- Psychological and mental health consequences
Episiotomy
An episiotomy is where the obstetrician or midwife cuts the perineum before the baby is delivered. This is done in anticipation of needing additional room for delivery of the baby (e.g. before forceps delivery). It is performed under local anaesthetic. A cut is made at around 45 degrees diagonally, from the opening of the vagina downwards and laterally, to avoid damaging the anal sphincter. This is called a mediolateral episiotomy. The cut is sutured after delivery.
Perineal Massage
Perineal massage is a method for reducing the risk of perineal tears. It involves massaging the skin and tissues between the vagina and anus (perineum). This is done in a structured way from 34 weeks onwards to stretch and prepare the tissues for delivery.
Last updated September 2020