Perineal tears

Perineal tears are more likely to occur with:

• precipitant labour
• shoulder dystocia
• forceps deliveries
• narrow suprapubic arch
• big babies
• babies with poorly flexed heads

Perineal injury remains the commonest form of maternal obstetric injury and had been traditionally classified into first, second and third degree (in the UK, a third-degree tear used to be recorded only if the anal sphincter was completely disrupted and the rectal mucosa was breached; in the USA, a tear that involved the anal sphincter to any degree was classified as third degree, and one that involved the rectal mucosa was called fourth degree). The classification used in the UK has been updated and now distinguishes first, second, third and fourth-degree tears (1):

• First-degree tear - tear involving the perineal or vaginal skin only
• Second-degree tear - perineal skin and muscles torn, but intact anal sphincter
• Third-degree perineal tear - perineal skin, muscles and anal sphincter are torn
  1. Less than 50% of the external anal sphincter thickness is torn
  2. More than 50% of the external anal sphincter thickness is torn, but internal anal sphincter intact
  3. Both external and internal anal sphincters are torn, but anal mucosa intact
• Fourth-degree perineal tear - perineal skin, muscles, anal sphincter and anal mucosa are torn
• Button-hole tear - anal sphincter is intact but anal mucosa is torn

Anatomically, an episiotomy involves the same structures as a second-degree perineal tear

Management depends on the type of tear:

General principles for management are:

• labial tear - uncomfortable; heal quickly; rarely require suturing
• first-degree tear - superficial; no involvement of muscle; may not require suturing if there is only minimal blood loss
• second-degree tear - involves perineal muscle and requires suturing
• third- and fourth-degree tears - require repair by an experienced surgeon

Prognosis (2,3,4):

First-degree tears

• superficial injury involving only the perineal skin or vaginal mucosa.
  • excellent prognosis - tissues heal rapidly and spontaneously, often within 1 to 2 weeks
  • suturing is frequently unnecessary unless required for haemostasis.
  • long-term structural or functional morbidity is rare

Second-degree tears and episiotomies

• anatomically, a standard episiotomy mirrors a second-degree tear
• initial surface healing and closure of the muscle bed typically occur within 2 to 4 weeks
• complete tissue remodelling and strength are expected by 4 to 6 weeks
  • episiotomies and second-degree tears significantly increase the probability of localised perineal pain and wound-healing problems at the third postpartum week compared to intact perineums

Third- and fourth-degree tears (obstetric anal sphincter injuries [OASI])

• severe injuries involving partial or total disruption of the anal sphincter complex (Third-degree), or extending through the anal mucosa (Fourth-degree)
• complete structural and muscular healing requires 6 to 12 weeks
• long-term tracking shows that between 15% and 61% of women continue to suffer varying symptoms of anal or flatus incontinence and chronic dyspareunia following primary repair (4)

Notes:

• a systematic review (5) noted that limited data available showed that, compared to immediate primary end-to-end repair of obstetric anal sphincter injuries, early primary overlap repair appeared to be associated with lower risks for faecal urgency and anal incontinence symptoms. However, the review noted that experience of the surgeon was not addressed in the studies reviewed, and therefore it would be inappropriate to recommend one type of repair in favour of another
• in the majority of cases either a first- or second-degree tear is sustained - serious sequelae are infrequent
• anal sphincter tears are a relatively uncommon occurrence on any delivery suite (4):
  • reported incidence varies considerably, but it is usually between 0.5% and 2.5% of vaginal deliveries
  • anal sphincter tears are an important risk factor for long-term anal sphincter dysfunction
    • up to 60% of women who sustain a sphincter tear are reported to experience symptoms of dyspareunia, perineal pain or anal incontinence

References:

1. Fernando RJ, Sultan AH. Risk factors and management of obstetric perineal injury. Curr. Obs. & Gynae. 2004; 14 (5):320-326.
2. Adanna Okeahialam N, Thakar R, Sultan AH. The clinical progression and wound healing rate of dehisced perineal tears healing by secondary intention: A prospective observational study. Eur J Obstet Gynecol Reprod Biol. 2022 Jul;274:191-196.
3. Lewin S et al. Wound Healing After Vaginal Delivery, Episiotomy, and Cesarean Section Delivery Among Women With IBD: Results From the PIANO Registry. Inflamm Bowel Dis. 2025 Aug 1;31(8):2106-2111.
4. Villot A et al. Prise en charge des périnées complets (déchirure périnéale stade 3 et 4) : revue de la littérature [Management of third and fourth degree perineal tears: A systematic review]. J Gynecol Obstet Biol Reprod (Paris). 2015 Nov;44(9):802-11.
5. Fernando R et al. Methods of repair for obstetric anal sphincter injury. Cochrane Database Syst Rev. 2006 Jul 19;3:CD002866.