Perineal Tears

Question 1

When do perineal tears occur

Answer 1

Occurs where the external vaginal opening is too narrow to accommodate delivery- this leads to the skin and tissues in that area tearing as the baby’s head passes

Question 2

What is the incidence of obstetric anal sphincter injury (OASIS-third and fourth degree perineal tears)

Answer 2

2.9% in the UK, with incidence of 6.1% in primiparae compared to 1.7% in multiparae.

Question 3

Classification of perineal tears

Answer 3

• First-degree tear: Injury to perineal skin and/or vaginal mucosa.
• Second-degree tear: Injury to perineum involving perineal muscles but not involving the anal sphincter.
• Third-degree tear: Injury to perineum involving the anal sphincter complex:
  o Grade 3a tear: Less than 50% of external anal sphincter (EAS) thickness torn.
  o Grade 3b tear: More than 50% of EAS thickness torn.
  o Grade 3c tear: Both EAS and internal anal sphincter (IAS) torn.
• Fourth-degree tear: Injury to perineum involving the anal sphincter complex (EAS and IAS) and anorectal mucosa
• Rectal buttonhole tear: Where the tear involves the rectal mucosa with an intact anal sphincter complex

Question 4

Risk factors for perineal tears

Answer 4

• Nulliparity, birthweight greater than 4Kg
• Asian ethnicity
• Occipito-posterior position
• Prolonged second stage of labour (greatest risk at a duration of more than 4 hours)
• Instrumental delivery (risk far greater in forceps delivery without episiotoy)

Question 5

Complications of perineal tears

Answer 5

• Short-term complications: pain, infection, bleeding, wound breakdown or dehiscence
• External anal sphincter incompetence leads to faecal urgency
• Internal anal sphincter incompetence leads to faecal incontinence
• Fistula, sexual dysfunction, psychological and mental health consequences are also possible

Question 6

What is the role for episiotomy in perineal tears

Answer 6

• Mediolateral episiotomy should be considered in instrumental deliveries
• Where episiotomy is indicated the mediolateral technique is recommended, with careful attention to ensure that the angle is 60 degrees away from the midline when the perineum is distended

Question 7

What other (aside from episiotomy) protective measures can be taken during delivery

Answer 7

• Perineal protection at crowning can be protective (this includes ‘hands on techniques’):
• 1. Left hand slowing down the delivery of the head. 2. Right hand protecting the perineum. 3. Mother NOT pushing when head is crowning (communicate). 4. Think about episiotomy (risk groups and correct angle)
• Warm compression during the second stage of labour reduces the risk of OASIS.
• All women having a vaginal delivery are at risk of sustaining OASIS or isolated rectal buttonhole tears. They should therefore be examined systematically, including a digital rectal examination, to assess the severity of damage, particularly prior to suturing. Explain the process of examination. Offer inhalational analgesia and ensure good lighting. The woman should usually be in the lithotomy position

Question 8

How should perineal tears be repaired

Answer 8

• 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 second-degree tear requires suturing on the ward by a suitably experienced midwife or clinician
• Repair of third and fourth degree tears should be conducted by a clinician in an operating theatre, under LA/GA. If there is excessive bleeding, a vaginal pack should be inserted and the woman should be taken to theatre as soon as possible
• Figure of 8 sutures should be avoided (haemostatic)- should use continuous or interrupted sutures
• 3-0 polyglactin should be used to repair the anorectal mucosa as it may cause less irritation and discomfort than polydioxanone (PDS) sutures
• When repair of the EAS and/or IAS muscle is being performed, either monofilament sutures such as 3-0 PDS or modern braided sutures such as 2-0 polyglactin can be used with equivalent outcomes
• The use of broad spectrum antibiotics is recommended postoperatively as well as the use of postoperative laxatives to reduce risk ofwound opening. Physiotherapy could be useful and women should be reviewed 6-12 weeks postpartum

Question 9

How should women be counselled in future pregnancy after perineal tears

Answer 9

• All women who have sustained OASIS in a previous pregnancy and who are symptomatic or have abnormal endoanal ultrasonography and/or manometry should be counselled regarding the option of elective caesarean birth

Question 10

What is the prognosis following an OASIS

Answer 10

• 60–80% of women are asymptomatic 12 months following delivery and EAS repair