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.
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.
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)
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.
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.
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.
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.
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.
HP Dietz, Sydney 2015, http://sydney.edu.au/medicine/nepean/research/obstetrics/pelvic-floor-assessment/English/sydney%20pelvic%20floor%20home%20page/newest/Sydney%20Pelvic%20Floor%20website%20home%20page%20html.html