Obstetric Anal Sphincter Injuries (OASIS) – Can I reduce my risk?

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Perineal tears can occur either spontaneously with vaginal delivery or as an extension to an episiotomy.

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Perineal tears are classified according to the extent of damage to the perineal structures:

1st degree tear - damage to the vaginal mucosa

2nd degree tear - damage to the vaginal mucosa and the perineal muscles

3rd degree tear - a partial or complete disruption of the anal sphincter complex which includes the external anal sphincter and the internal anal sphincter

4th degree tear - disruption of the anal sphincter complex as well as the anal mucosa

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Obstetric anal sphincter injuries (OASIS) include 3rd and 4th degree perineal tears.

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Risk factors associated with 3rd and 4th degree perineal tears

■ Women having their first vaginal birth

■ Women of South Asian ethnicity

■ Infants with a higher birth weight (> 3.5 kg)

■ Persistent foetal posterior position

■ Prolonged second stage of labour

■ Instrumental birth (forceps, vacuum)

■ Epidural

■ Midline episiotomy

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Can I reduce my risk of having an OASIS?

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Our women's health physios in Cammeray, Bondi Junction and the Shire (Woolooware) work with women to reduce their risk of OASIS using the latest evidence-based practise in combination with years of clinical experience.

During your ante-natal assessment, we will discuss the relevant risk factors including any prior birth history. We will assess your pelvic floor for its strength, resting tone, ability to relax and to distend “push” as it needs to during the second (pushing) stage of labour.

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Based on your assessment, we will commence specific pelvic floor muscle training to prepare you for labour and birth to reduce the risk of a 3rd or 4th degree perineal tear. This may involve down-training of your pelvic floor by performing soft tissue releases and teaching you to relax and release tension using breath and mindfulness, or strengthening the muscles and working on timing and co-ordination. We will practice with you how to push well and with control during labour. We will discuss positions to labour and birth in and how to modify these depending on how the labour progresses. We will teach you how to perform perineal massage (after 34 weeks of pregnancy) which can help protect your perineum and reduce the risk of 3rd and 4th degree tears.

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How are OASIS managed?

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3rd and 4th degree tears require surgical repair.

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An immediate post-operative complication can be perineal pain which can lead to urinary retention and defecation problems. It can also cause problems such as dyspareunia (pain with intercourse), faecal and flatal incontinence and faecal urgency in the long -term.

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Early management in the hospital will involve regular analgesia, application of ice to the area, keeping the stitches clean and dry, and positioning to prevent pressure on the stitches. Gentle pelvic floor muscle activation may aide healing by increasing circulation to the area. Activities that increase the intra-abdominal pressure and exert a downward pressure on the perineum should be minimized where possible, such as lifting a young child or a baby capsule. Activating the pelvic floor muscles prior to coughing, sneezing, laughing, lifting and avoiding constipation and straining can help to protect the stitches.

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You will be advised to see a women’s health physiotherapists at 4-6 weeks post-partum to assess your recovering pelvic floor. Here at The Physiotherapy Clinic, we specialise in pelvic floor and post-natal rehabilitation for women with 3rd and 4th degree perineal tears. We will listen sensitively to your birth story and assess your pelvic floor to determine whether there is a bladder and/or bowel dysfunction, problems with intercourse or pelvic organ prolapse. We will work with you to devise a plan and guide you through lifestyle modifications, exercise and manual therapy to achieve your short-term and long-term goals. We will communicate with the other health professionals involved in your care and keep them updated of your progress and recovery. We will arrange referrals other specialists such as psychologists or sex therapists based on your individual need.

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If you are concerned that you may be at risk for a perineal injury or would like to see a women’s health physiotherapist for an ante-natal or post-natal assessment of your pelvic floor or have sustained a 3rd or 4th degree perineal tear, reach out to us at any one of our clinics in Cammeray, Bondi Junction, the shire (Woolooware). We would be happy to assist you through your pregnancy and post-natal journey.