Birth-related pelvic floor injury is among the most common causes of long-term morbidity in young women. It also often generates claims in which the key questions are specialist ones about what the injury is, what caused it, and what it will mean in 20 years. 

The Scale of The Problem 

Obstetric anal sphincter injury (OASI), a third- or fourth-degree perineal tear, affects around 3% of vaginal births in the UK. The rate is about 6% in first vaginal births. OASI is only the most visible part of a wider spectrum of injury. It sits alongside: 

• levator ani avulsion, the detachment of the puborectalis muscle from the pubic bone 
• pudendal nerve injury 
• damage to the urethral sphincter  

These injuries are underdiagnosed at the time of delivery. They often present months or years later as faecal or flatal incontinence, urinary incontinence, pelvic organ prolapse, or sexual dysfunction. 

For lawyers, this creates a recurring problem. The birth is managed by obstetricians and midwives, but the consequences are assessed, investigated and treated by urogynaecologists and colorectal surgeons. A claim built only on obstetric evidence can establish that something went wrong in the delivery room. It may still leave the court with little reliable basis for deciding what that failure actually caused. 

Where Breach Usually Lies 

Most allegations fall into four categories: 

1. Intrapartum management. Examples include inappropriate choice or counselling for mode of delivery, inappropriate conduct of instrumental delivery, failure to protect the perineum, or poorly judged episiotomy. 
2. Failure to recognise the injury. Every woman who has had a vaginal delivery should have a systematic perineal and rectal examination. Many so-called "occult" sphincter defects found on later endoanal ultrasound are now understood to have been clinically detectable tears that were missed. 
3. Inadequate repair. This covers the technique, suture material, setting and seniority of the operator, measured against RCOG Guidance and local protocols. 
4. Failures after the birth. These include inadequate follow-up, physiotherapy referral or investigation, and poor counselling about the mode of any future delivery. 

Consent now runs through all four. After Montgomery, the question is whether a woman was told about material risks. For a woman with a large baby, a previous OASI or significant symptoms, those risks include the pelvic floor consequences of vaginal birth compared with caesarean section. The obstetric or midwifery expert is the right witness for breach in the delivery room. The questions that follow are usually outside their day-to-day practice. 

Causation: The Counterfactual Problem 

Causation in pelvic floor cases is rarely straightforward, because vaginal birth itself carries a substantial baseline risk of pelvic floor dysfunction. Even with impeccable care, a proportion of women delivering vaginally sustain OASI, and a larger proportion sustain trauma leading to urinary incontinence or prolapse. Pregnancy alone, whatever the mode of delivery, is also associated with later urinary incontinence and prolapse. 

So the causation expert must separate three things: 

• Injury that would have happened anyway. The tear or avulsion may have been unavoidable, and the negligence lies elsewhere. 
• Injury caused or worsened by the breach. For example, a sphincter defect that persists because a tear was missed or poorly repaired, when a competent primary repair would probably have given a good functional result. 
• Symptoms from unrelated or later factors. These include subsequent deliveries, menopause, obesity, chronic constipation, and ageing. 

The evidence base does support some of these distinctions. After a recognised OASI with a competent primary repair, most women (roughly 60–80% in the published series) are asymptomatic at 12 months. Outcomes after a missed or delayed diagnosis are materially worse. That difference is often the heart of the claim. 

Quantifying the difference for an individual claimant needs objective investigation: 

• endoanal ultrasound to show the extent and site of any residual sphincter defect 
• anorectal physiology testing 
• where urinary symptoms are prominent, urodynamic bladder tests 

Validated symptom scores put the reported symptoms on a defensible footing. 

Prognosis: Thinking in Decades 

Condition and prognosis reports in these cases carry substantial value, because claimants are often in their twenties or thirties. The expert must address: 

• Future treatment. This includes pelvic floor and biofeedback physiotherapy, sacral neuromodulation, secondary sphincter repair, and continence or prolapse surgery. Each has realistic success rates and a risk of failure or repeat surgery over a lifetime. 
• Future pregnancies. The RCOG advises that women with persisting symptoms or significant defects on investigation should be counselled about elective caesarean section. This affects both the claimant's reproductive choices and the costs. 
• Menopause. Declining oestrogen and ageing tissues commonly unmask or worsen a compensated sphincter or support defect. A woman who is coping at 35 may not be coping at 55, and the report should say how likely that is. 
• Sexual function, psychological sequelae and effects on employment. These often require referral to a psychiatrist or psychologist. 

When to Instruct a Urogynaecologist 

Instruct a urogynaecologist for causation and condition and prognosis evidence where: 

• the claim involves continuing bowel, bladder, prolapse or sexual symptoms, and not only the circumstances of the delivery 
• the key issue is what a competent repair would have achieved, or whether an alleged defect exists at all 
• investigations need to be commissioned or interpreted 
• the claimant is young, so that lifetime prognosis, future surgery and future deliveries drive quantum 
• the defence argues that symptoms reflect background risk, later births or unrelated conditions 

Where faecal incontinence dominates, joint instruction with a colorectal surgeon may be appropriate. The two disciplines complement each other.