How common are 3rd & 4th Degree tears (OASIS - Obstetric Anal Sphincter Injury)?​

• Over 75% of mums experiencing vaginal births for the first time will have a birth tear, most are 2nd degree. 

• According to The Royal College of Obstetrics and Gynecology (RCOG) birth tears occur in 3 in 100 births. Slightly more in first time births (6 in 100) and slightly less in subsequent ones (2 in 100). 

• However, some faculties such as the Nepean Clinical School in Sydney University Australia, run by Dr Dietz, have estimated severe tears to occur at much higher levels: somewhere between 10-20 in 100 births. This is due to some tears not being accounted for or misdiagnosed at the time of birth. Severe tears are also on the increase.

• Dr Dietz also estimates that the risk of an anal tear for first time mothers over the age of 38 is 15%. Some can go undiagnosed and not found until later, which can distort the statistics. 

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What increases the risk of severe tearing?

The risk increases with:​

• first time birth

• baby weighing over 4kg (8lbs 13oz)

• if the second stage of labour (when fully dilated) is 2 hours or more.

• forceps delivery

• if you've suffered a 3rd or 4th degree tear before 

• shoulder dystocia during labour 

• laying down during 2nd stage/pushing stage or a low squatting position when crowning (results from a small study in Sweden)

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I've just had a birth tear. When should the pain go away?

It varies. However, if you are in severe pain after 1 or 2 weeks, this isn't normal and you need to speak to a medical professional. Mild pain can go on for a couple of months, specifically while sitting. If mild pain persists past 6-8 weeks, go and speak to your doctor.

You may need a referral to a women's health phsyio. 

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Are there any long-term complications/issues?

There are immediate complications such as developing a recto-vaginal fistula or an infection. These are uncommon however and tend to occur if a tear goes undiagnosed/missed at birth. 

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60-80% of women are symptom-free at 12 months postpartum. However, some women still have incontinence, pain, and/or numbness/nerve damage.

If any of these worry you, please speak to your medical professional. 

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Which method of birth should I have next time?

Every birth and tear is different. Some women heal very quickly and have no ongoing problems, whereas others can have a very hard time and go on to have lasting damage. Women go on to have vaginal births and Elective Caesarians after suffering with a birth tear.

The NHS does provide more options for women who have suffered an OASIS.

We also have a page on our website dedicated to this question here. 

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What is the risk for another severe tear for subsequent vaginal births?

The risk is higher for women who have already suffered a severe tear. 5-7% compared to 2% for the women who had an uncomplicated vaginal birth. Again, we have more info on this here.