Obstetric anal sphincter injury (OASI) can occur during vaginal delivery and is a severe injury to the perineum. It is the collective term for grade 3-4 perineal tears that may occur during delivery. What this means is that the perineal tissues can tear from the vaginal entrance to the anal sphincter. Depending on the depth of the tear, will depend on the grade you would receive. In 2011 the English National Health Institute reported that 5.9% of primiparous women suffered an OASI after birth.

Risk factors for OASI are:

  • Birth weights over 4kg
  • Primiparity
  • Assisted birth (instrument use)

Women with an OASI may experience:

  • Incontinence
  • Sexual dysfunction
  • Chronic pain
  • PTSD

Surgery is required to fix the perineal muscles to ensure that they heal correctly in the postpartum period. (The Royal Women’s Hospital) This will happen within the first 8-12 hours after delivery. (Harvey,M etal 2015)

What does this mean for future babies?
If you choose to have more children, the research has shown that if you have had an OASI in the past it increases your risk of a recurrent OASI in the future. (The Royal Women’s Hospital)

How Can I Prevent Tearing? (Harvey,M. Etal  2015)

  • Hands on Perineal support while delivering.
  • Warm compress to perineal area while delivering.
  • Sitting or kneeling for delivery decreases the risk compared to standing.
  • If required a mediolateral episiotomy

To prevent the risk of experiencing an OASI, The Royal College of Obstetrics and Gynecologists and the Royal College of Midwives devised a project to help decrease the risk of OASI in women during delivery. The following points are recommended for women during pregnancy and delivery.

  • Antenatal education surrounding OASI and how to reduce risk.
  • When indicated an episiotomy should be utilised.
  • Use of manual perineum protection (hands on the perineum providing pressure)
  • Doctor to check for tears of the perineum after delivery.

How can Physiotherapy help me after an OASI?
An assessment from a Women’s health physiotherapist is highly recommended if your obstetrician or midwife has told you that you have an OASI. Your women’s health physiotherapist has the training to help in your recovery of an OASI. In that appointment they can give you an individualised rehabilitation program for your pelvic floor and perineum.

Here are some helpful tips that can get you through your first 6 weeks of recovery:

  • Keep the area clean.
  • Avoid straining in the bathroom.
  • Avoid constipation.
  • Practice good toileting positions: poo stools, being relaxed, no straining, leaning forwards.
  • Light pelvic floor exercises to help stimulate blood flow to the area.
  • Cool compress to help with inflammation.
  • Avoid heavy lifting.

If you are at all concerned, contact our physiotherapists at Bump Fitness to help guide you on your recovery journey.


Bidwell P, Sevdalis N, Silverton L, Harris J, Gurol-Urganci I, Hellyer A, Freeman R, van der Meulen J, Thakar R. Women’s experiences of the OASI Care Bundle; a package of care to reduce severe perineal trauma. Int Urogynecol J. 2021 Jul;32(7):1807-1816. doi: 10.1007/s00192-020-04653-2. Epub 2021 Jan 21. PMID: 33475817; PMCID: PMC8295065.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8295065/

D’Souza JC, Monga A, Tincello DG, Sultan AH, Thakar R, Hillard TC, Grigsby S, Kibria A, Jordan CF, Ashmore C. Maternal outcomes in subsequent delivery after previous obstetric anal sphincter injury (OASI): a multi-centre retrospective cohort study. Int Urogynecol J. 2020 Mar;31(3):627-633. doi: 10.1007/s00192-019-03983-0. Epub 2019 Jun 22. PMID: 31230097; PMCID: PMC7093337.https://pubmed.ncbi.nlm.nih.gov/31230097/

Harvey,M & Pierce,M 2015. Obstetrical Anal Sphincter Injuries (OASIS): Prevention, Recognition, and Repair. Journal of Obstetrics and Gyancology Canada. DOI:https://doi.org/10.1016/S1701-2163(16)30081-0.https://www.jogc.com/article/S1701-2163(16)30081-0/fulltext


James Padget University Hospital ..Physiotherapy advice and exercises for OASI. https://www.jpaget.nhs.uk/media/361795/PH-38-Physiotherapy-Advice-and-Exercises-for-Obstetric-Anal-Sphincter-Injury-OASI-v1-web.pdf

Image reference https://www.embracephysio.sg/obstetric-anal-sphincter-injuries-oasis-how-womens-health-physiotherapy-can-help/