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Firstly, it is normal for the perineum ( skin in-between front and back passage) to tear to some extent during child birth. 90% of women will experience some sort of graze or tear. It is more common to tear around the perineum, however more rarely; some ladies will tear on the labia, clitoris, urethra and inside the vagina. Less common is an obstetric anal sphincter injury (OASI) which affects approximately 5% of all normal vaginal deliveries. Below is the classification of tears


Labial Lacerations (often referred to as labial grazes): Small tears to the superficial muscles, some require suturing, some don’t depending on the severity.

  • First degree tear: Superficial tears of the skin, and/or tissue and/or vaginal mucosa. Suturing is either optional or advised depending on the severity.

  • Second degree tear: Deeper tear to the perineal body and sometimes involving the pelvic floor muscles (levator ani). Suturing is usually required and encouraged unless declined.

  • Third-degree tear: Injury to perineum involving the anal sphincter complex:

  • Grade 3a tear: Less than 50% of external anal sphincter (EAS) thickness torn.

  • Grade 3b tear: More than 50% of EAS thickness torn.

  • 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 ano rectal mucosa.



The word OASIS encompasses both third and fourth degree perineal injuries, all of which are usually sutured/repaired in theatre by a consultant.


Common risk factors associated with sustaining an OASI include the following:

  • Nulliparity ( delivering your first baby vaginally,) includes vaginal birth after section (VBAC)

  • Birth weight of a baby weighing over 4kg

  • Shoulder Dystocia

  • Prolonged second stage of labour

  • Quick second stage of labour

  • Instrumental delivery ( use of forceps / vount extraction)

  • Asian ethnicity

If you have any concerns following your delivery, the healing process and/or current symptoms then physiotherapy to the pelvic floor can really help. 

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