Obstetric Anal Sphincter Injuries (OASIs): The Women’s Health Physiotherapy Treatment

Congratulations, you’re pregnant! All those antenatal classes and conversations with friends have likely reached the topic of perineal tearing, sending shivers down your spine, and making you think, ‘I’m never going to be the same again…’

The fear of perineal tears is real. However, the most effective way to address it is through open conversation and strategies to minimise the risk. Birth is a natural process, and many women have given birth even without medical intervention. Having this information shouldn’t change the desire for a natural birth; instead, it can empower you to actively participate in your delivery.


A perineal tear is an injury to the perineum, the region between the vagina and the anus. Approximately 85% of women undergo some degree of perineal trauma during vaginal childbirth, though not all births cause significant injury. First and second-degree tears are frequent, often requiring stitches, but women generally recover within a few weeks or months. An episiotomy is equivalent to a grade 2 perineal tear, involving some tissue and superficial muscle tearing.


An obstetric anal sphincter injury (OASIS) pertains to third and fourth-degree perineal tears or more severe trauma. These tears extend from the perineum to the anus or rectum and involve the muscles responsible for controlling the opening and closing of the anus.

A Grade 3 tear entails changes to the anal sphincter muscles and is further categorised as:

  • 3A: where <50% of the external anal sphincter is torn,
  • 3B: where >50% of the external anal sphincter is torn,
  • 3C: where both the external and internal anal sphincters are torn

Meanwhile, a Grade 4 tear involves changes to the internal and external anal sphincters, along with the mucosa, or the lining of the rectum.


Image credit: mypfm.com


Approximately 5% of women having their initial vaginal birth and 3% of multiparous women will undergo a third or fourth-degree perineal tear. While most women experiencing these tears recover well with suitable treatment and support, some may require specialised care for optimal recovery.

Women suffering from OASIs often report symptoms such as faecal urgency, flatulence, and faecal incontinence. Perineal pain and/or dyspareunia (pain during intercourse) may also be experienced. All instances of OASIs necessitate surgical repair conducted by an experienced surgeon in an operating theatre, under good lighting and either regional or general anaesthesia.



Women having their first-ever vaginal delivery, those of South Asian ethnicity, or those delivering babies heavier than four kilograms, face an increased risk of experiencing a third or fourth-degree tear. Additional risk factors during labour include a persistent occiput-posterior position, an extended second stage of labour, shoulder dystocia, a midline episiotomy, and/or an instrumental vaginal delivery.


  • Maintain a healthy lifestyle during your pregnancy. (Hey! We host prenatal group exercise classes!)
  • Start perineal massage from 34 weeks, twice a week for 10 minutes.
  • Apply a warm compress to the perineum during the second stage of labour.
  • Control the pace at which the baby’s head and shoulders emerge, with guidance from your birth attendant.
  • Attend an appointment with your women’s health physiotherapist during pregnancy to learn how to prepare your pelvic floor for delivery.


Effective management of pain and swelling is crucial. Painkillers and laxatives are usually prescribed to ease bowel movements, and antibiotics may be given to lower the infection risk. Using ice packs on the perineum during the first 72 hours is recommended to aid healing. Sitting with a soft cushion beneath the thighs can relieve pressure on the perineum, enhancing comfort, particularly when feeding the baby. Adopting the side-lying position while feeding may also alleviate strain on the recovering perineum.

You may encounter challenges with your bladder and bowel. It’s common to experience difficulty controlling gas or stool, urgency in bladder and/or bowel movements, and discomfort during intercourse. If these symptoms persist beyond six weeks, it is advisable to consult your women’s health physiotherapist.


Your women’s health physiotherapist can help postnatally by:

  • Conducting an assessment, typically involving a pelvic floor examination.
  • Aiding in preparing your pelvic floor for delivery to reduce the risk of tearing.
  • Providing advice on the management of perineal tears or episiotomies, incorporating hands-on therapy on the tear or wound, ultrasound, massage, and stretching techniques.
  • Teaching you how to urinate (voiding dynamics) and proper bowel movement (defecation dynamics)
  • Prescribing a pelvic floor muscle training program designed to strengthen the sphincter and pelvic floor muscles, or, in certain cases, assist in relaxing these muscles.

If you are recovering from a perineal tear or episiotomy and require care, please call or WhatsApp us at 9780 7274, or email us at help@embracephysio.sg to discuss the treatment you need.

Feel free to look through our website, where you can learn about other women’s health conditions we treat. This is a safe space where we can discuss how we can help you with physiotherapy.

Note: While I am a physiotherapist, I am not your personal physiotherapist. The contents of this website are for informational purposes only and are not intended to serve as individual medical advice.


  1. Australian Commission on Safety and Quality in Healthcare. 2021. Third and Fourth Degree Perineal Tears Clinical Care Standard. [online] Available at: <https://www.safetyandquality.gov.au/standards/clinical-care-standards/third-and-fourth-degree-perineal-tears-clinical-care-standard?fbclid=IwAR0H_P9TL7j_RP9mC8fPucl1MvGuXXvua91sIY70-rmp-5tjELZLAEWLl9Q> [Accessed 29 April 2021].
  2. Beckmann MM, Stock OM. Antenatal perineal massage for reducing perineal trauma. Cochrane Database of Systematic Reviews 2013, Issue 4. Art. No.: CD005123. DOI: 10.1002/14651858.CD005123.pub3. Accessed 24 May 2021
  3. https://www.embracephysio.sg/what-is-a-pelvic-floor-exam/
  4. https://www.embracephysio.sg/classes
  5. https://www.embracephysio.sg/what-is-a-perineal-tear-and-episiotomy/#content
  6. https://www.jogc.com/article/S1701-2163(16)30081-0/fulltext
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I had a pleasant experience with the team at Embrace. The receptionist Su is very warm and always ready to help! My therapist was Brenda. I went due to pregnancy pains and post partum diastasis recti. Throughout my pregnancy and DR recovery, she recommends tailored exercises and ensures any difficulty that I had are always addressed. She also prepared me for my birth experience and not forgetting the tension releases that felt so good! It was my first time engaging a physiotherapist and it’s worth it. I’ve learnt a lot and I’m more confident of doing the exercises at home now that I’ve been “discharged”

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