Our Service For You

Birth Injury Articles
Perineal Tears  What are OASIS?

Perineal Tears What are OASIS?

Medical terminology can be confusing and unhelpful. If you have suffered an injury during childbirth, clarity of language is vital to your understanding.

What is a perineal tear?

A perineal tear is a wound to the skin and/or muscle that sometimes occurs naturally during vaginal childbirth. As the baby emerges via the vagina, the surrounding skin will need to expand to allow the completion of delivery and this may cause the skin to split. A perineal tear might only affect the skin around the vagina, or it may also damage the tissue of the perineum, between the vagina and anus. At its worst, a perineal tear might also affect the muscle and lining of the anus.

What are OASIS?

OASIS stands for Obstetric Anal Sphincter Injuries. This refers to the most severe form of perineal tear, otherwise known as 3rd or 4th degree tears. The term indicates an injury which, in addition to damaging the skin and tissue of the perineum (a 2nd degree tear), also damages the anus to some degree.

Why are OASIS a problem?

Explaining the impact of anal sphincter injuries.

The anal sphincter controls the passing of faeces and wind. It is the muscles (internal and external) which relax or contract in order to empty our bowels or to prevent the escape of wind. If these muscles are damaged and do not function effectively, we can lose the ability to control the anus and become incontinent. This means that we cannot stop the passing of faeces or wind.

If the anal sphincter is damaged by a natural tear during childbirth, a third degree tear or OASI, has occurred. This needs to be fully repaired in an operating theatre soon after the birth to ensure a good recovery. Without such treatment, the victim can experience on-going incontinence.

Injury to the anal lining

If the internal lining of the anal canal is also damaged, this is called a 4th degree tear and is more serious again. If such an injury is not identified at the time of the birth, or is poorly repaired, a hole (or fistula) can develop between the interior of the anus and the perineum or vagina, meaning that faeces can involuntarily leak between these two parts of the body.

This can be extremely distressing and embarrassing. It can also lead to permanent damage and incontinence.

Treatment of OASIS

Regarding the diagnosis of severe tears, the guidelines of the Royal College of Obstetricians and Gynaecologists state the following:

'All women having a vaginal delivery are at risk of sustaining OASIS. They should therefore be examined systematically, including a digital rectal examination, to assess the severity of damage, particularly prior to suturing.'

In relation to repair, the guidelines go on to say:

'Repair of third and fourth degree tears should be conducted by an appropriately trained clinician or by a trainee under supervision.

Repair should take place in an operating theatre, under regional or general anaesthesia, with good lighting and with appropriate instruments. If there is excessive bleeding, a vaginal pack should be inserted and the woman should be taken to theatre as soon as possible.'

Medical Negligence

If an OASI or severe tear is sustained and examination, diagnosis and treatment do not take place promptly, the mother may experience long-term physical symptoms. In these circumstances, she may have been the victim of medical negligence and could be entitled to make a claim for substandard medical care.

Glynns Solicitors specialise in medical negligence compensation claims. We have considerable experience of supporting claims for inadequate treatment of perineal tears. Contact us to discuss your circumstances if you are suffering the effects of this distressing injury.

Please call us on 0800 234 3300 (or from a mobile 01275 334030) or complete our Online Enquiry Form.

Free enquiry

Free Claim Enquiry

Complete a short enquiry form and we will contact you.

Free enquiry



"Before we contacted you we had no real idea that we had grounds for a medical negligence claim but after speaking to you if became clear that Wendy was indeed treated poorly. Chris took the time to explain what was happening and kept us to speed. Our deepest gratitude to you all and Chris in particular."

"I would like to say a big thank you to you for making this whole process easy and relatively painless. You kept me informed throughout and you were always polite and courteous in all forms of communication. I would not hesitate to recommend you to friends and family, so a really big thank you and I wish you all the best in the future."

» Read More Medical Negligence Testimonials?


Our Expertise

clinical negligence panel


Free Birth Injury Guide

Helping Clients throughout England and Wales

contact us