Perineal trauma: episiotomy, second-degree repair and OASIS

The baby is on her chest and the room has relaxed. You have a good light, a stack of swabs and a midwife who says "just a second-degree, I think". This is the moment the whole topic turns on — because the difference between a 3a tear repaired properly tonight and a 3a tear called second degree is a woman who leaks flatus at her daughter's school gate in fifteen years. Put a finger in the rectum before you put a needle in the perineum.^[1][14]

Overview and definition

Perineal trauma is graded by what is torn, not by how it looks or how much it bleeds. ^[1]

• The scale that matters is the one described by Sultan, adopted by the International Consultation on Incontinence and by the RCOG, and used across Australia and New Zealand.^[1][18]
• OASIS — obstetric anal sphincter injury — is the umbrella term for third- and fourth-degree tears together. Use the acronym precisely; examiners notice when candidates use it to mean only third degree.^[1]
• Anal incontinence is the involuntary loss of flatus and/or faeces that affects quality of life. Flatus counts. A woman who cannot hold wind is symptomatic.^[14][19]

One anatomical footnote earns marks: the lining of the anal canal changes along its length, columnar proximally and modified squamous over the distal 1 to 1.5 cm, which is why the guideline term is anorectal mucosa rather than anal epithelium.^[1][20]

References20ShowHide

1. [1]Committee on Practice Bulletins-Obstetrics ACOG Practice Bulletin No. 198: Prevention and Management of Obstetric Lacerations at Vaginal Delivery Obstet Gynecol, 2018.PMID 30134424
2. [2]Fernando RJ, Sultan AH, Kettle C, et al. Methods of repair for obstetric anal sphincter injury Cochrane Database Syst Rev, 2013.PMID 24318732
3. [3]Fernando RJ, Sultan AH, Kettle C, et al. Repair techniques for obstetric anal sphincter injuries: a randomized controlled trial Obstet Gynecol, 2006.PMID 16738150
4. [4]Kettle C, Dowswell T, Ismail KM Continuous and interrupted suturing techniques for repair of episiotomy or second-degree tears Cochrane Database Syst Rev, 2012.PMID 23152204
5. [5]Kettle C, Dowswell T, Ismail KM Absorbable suture materials for primary repair of episiotomy and second degree tears Cochrane Database Syst Rev, 2010.PMID 20556745
6. [6]Eogan M, Daly L, O'Connell PR, et al. Does the angle of episiotomy affect the incidence of anal sphincter injury? BJOG, 2006.PMID 16411997
7. [7]Gurol-Urganci I, Cromwell DA, Edozien LC, et al. Third- and fourth-degree perineal tears among primiparous women in England between 2000 and 2012: time trends and risk factors BJOG, 2013.PMID 23834484
8. [8]Gurol-Urganci I, Bidwell P, Sevdalis N, et al. Impact of a quality improvement project to reduce the rate of obstetric anal sphincter injury: a multicentre study with a stepped-wedge design BJOG, 2021.PMID 33426798
9. [9]Jiang H, Qian X, Carroli G, et al. Selective versus routine use of episiotomy for vaginal birth Cochrane Database Syst Rev, 2017.PMID 28176333
10. [10]Buppasiri P, Lumbiganon P, Thinkhamrop J, et al. Antibiotic prophylaxis for third- and fourth-degree perineal tear during vaginal birth Cochrane Database Syst Rev, 2014.PMID 25289960
11. [11]Duggal N, Mercado C, Daniels K, et al. Antibiotic prophylaxis for prevention of postpartum perineal wound complications: a randomized controlled trial Obstet Gynecol, 2008.PMID 18515507
12. [12]Eogan M, Daly L, Behan M, et al. Randomised clinical trial of a laxative alone versus a laxative and a bulking agent after primary repair of obstetric anal sphincter injury BJOG, 2007.PMID 17516966
13. [13]Mahony R, Behan M, O'Herlihy C, et al. Randomized, clinical trial of bowel confinement vs. laxative use after primary repair of a third-degree obstetric anal sphincter tear Dis Colon Rectum, 2004.PMID 14719145
14. [14]LaCross A, Groff M, Smaldone A Obstetric anal sphincter injury and anal incontinence following vaginal birth: a systematic review and meta-analysis J Midwifery Womens Health, 2015.PMID 25712278
15. [15]Carter E, Hall R, Ajoku K, et al. Caesarean section and anal incontinence in women after obstetric anal sphincter injury: A systematic review and meta-analysis BJOG, 2025.PMID 38965793
16. [16]Mørch EJ, Perslev K, Wrønding T, et al. Counseling women with obstetric anal sphincter injury - Risk of recurrence and the influence of mode of second delivery on subsequent anal incontinence - A systematic review and meta-analysis Eur J Obstet Gynecol Reprod Biol, 2025.PMID 40090037
17. [17]Okeahialam NA, Wong KW, Thakar R, et al. The incidence of wound complications following primary repair of obstetric anal sphincter injury: a systematic review and meta-analysis Am J Obstet Gynecol, 2022.PMID 35550375
18. [18]Roper JC, Amber N, Wan OYK, et al. Review of available national guidelines for obstetric anal sphincter injury Int Urogynecol J, 2020.PMID 32789813
19. [19]Nilsson IEK, Åkervall S, Molin M, et al. Severity and impact of accidental bowel leakage two decades after no, one, or two sphincter injuries Am J Obstet Gynecol, 2023.PMID 36513133
20. [20]Roper JC, Thakar R, Sultan AH Isolated rectal buttonhole tears in obstetrics: case series and review of the literature Int Urogynecol J, 2021.PMID 32930849