Third- and fourth-degree tears (obstetric anal sphincter injury) after childbirth

NICE defines perineal trauma by depth. A first-degree tear involves the skin only and a second-degree tear involves the perineal muscles but not the anal sphincter. A third-degree tear goes through the anal sphincter complex and is divided into 3a (less than half of the external sphincter torn), 3b (more than half torn) and 3c (the internal sphincter also torn). A fourth-degree tear involves both sphincters and the lining of the anus.

The RCOG also describes a rare rectal buttonhole, in which the sphincter is intact but there is a hole between the back passage and the vagina. Passing wind or stool through the vagina is not normal, and anyone who notices it should see a healthcare professional urgently.

The RCOG reports that about 3 in 100 women having a vaginal birth in the UK have an OASI, rising to 6 in 100 at a first vaginal birth. A Scottish study of more than 182,000 first births found that third- or fourth-degree tears rose from 1 per cent in 1997 to 4.9 per cent in 2010.

The RCOG lists forceps birth, a baby heavier than 4 kg and Asian ethnicity as risk factors for a repeat tear, and the Scottish study found older maternal age and birthweight of 4,500 g or more were linked with repeat injury. NHS information on episiotomy notes that up to 9 in 10 first-time mothers who give birth vaginally have some tear, graze or episiotomy, and that an episiotomy may prevent a severe tear in some births, particularly forceps deliveries.

NICE intrapartum guidance recommends offering a warm wet compress to the perineum once the baby's head distends it, or perineal massage with water-soluble lubricant if preferred, and says routine episiotomy should not be done at spontaneous vaginal birth. If an episiotomy is needed, for example for forceps or ventouse birth or fetal compromise, a mediolateral cut at 45 to 60 degrees is recommended. The 2025 update adds that water birth may be associated with a lower risk of severe tears in women who have had a baby before.

The OASI Care Bundle, tested in 16 maternity units across England, Scotland and Wales, combined antenatal information, manual perineal protection and episiotomy when clinically indicated, plus a rectal examination after birth. OASI rates fell from 3.3 per cent to 3.0 per cent, a 20 per cent reduction in adjusted odds, without changes in caesarean or episiotomy rates. The NHS adds that midwives can guide the pace of the baby's head, and that perineal massage in the last weeks of pregnancy may reduce the chance of an episiotomy.

NICE says every woman should be offered a systematic assessment after birth, including a rectal examination, with good light, analgesia and gentle explanation. If an anal sphincter injury is found, the repair is done as soon as possible in theatre by an appropriately trained clinician, and NICE says staff should keep their repair skills up to date. The RCOG explains that you will need an epidural or spinal anaesthetic, rarely a general anaesthetic, a drip, and probably a catheter until you can walk to the toilet.

After the operation you should be offered pain relief such as paracetamol and ibuprofen, advised to take a course of antibiotics to reduce infection risk and laxatives to make opening your bowels easier, and offered a physiotherapy appointment. Rarely another operation is needed. Breastfeeding is not prevented by any of the treatments, although some women prefer positions other than sitting.

Soreness is expected for 4 to 6 weeks, particularly when walking or sitting, and stitches around the sphincter may be felt for up to 3 months. The RCOG advises washing daily with water only, changing pads regularly, drinking plenty of fluid, eating a healthy balanced diet and using a footstool to raise the knees when opening the bowels. Pelvic floor exercises should start as soon as possible, and strenuous activity or heavy lifting should be avoided for 4 to 6 weeks.

Worsening pain, smelly discharge, bleeding or red swollen skin around the wound can signal infection and should prompt contact with the midwife or GP. Follow-up is usually at 6 to 12 weeks, when you will be asked about bowel control and can discuss the birth. If symptoms continue after 6 months you should see a healthcare professional again.

The RCOG says a small number of women experience anal incontinence, meaning difficulty controlling the bowels or holding in wind, and that specialist physiotherapy or surgery is available. Anyone with symptoms should expect referral to a specialist team rather than being told to put up with them.

Sex can be uncomfortable at first. The RCOG says you can have sex when the stitches have healed, bleeding has stopped and it feels right, that water-based lubricant may help, and that persistent pain should be raised with a professional. It also warns of a risk of post-traumatic stress after a distressing birth, and encourages anyone with anxiety or low mood to ask for help.

The RCOG says that if you have recovered well and have no symptoms you may wish to consider a vaginal birth, whereas women with continuing symptoms may prefer a planned caesarean. It suggests women who had a third- or fourth-degree tear at a first birth have a 7 to 10 in 100 chance of a similar tear in the next vaginal birth. NICE, in guidance dating from 2007, states that the risk of repeat severe trauma is not increased compared with a first baby, so evidence is not settled and the numbers differ between sources.

NICE says a discussion about future mode of birth should cover current urgency or incontinence symptoms, the degree of previous trauma, the risk of recurrence, the success of the repair, the psychological effect of the trauma and management of labour, and that episiotomy should not be offered routinely after a previous severe tear. In the Scottish study, women with an earlier tear were over four times more likely to have a repeat tear in a second vaginal birth and about twelve times more likely to have an elective caesarean, so many women choose planned caesarean.