Insight

What OASI Litigation Teaches Us About Safer Maternity Care

Obstetric anal sphincter injuries (OASIs) are officially recorded in around 3 in 100 vaginal births in the UK, and in roughly 6 in 100 first‑time vaginal births. However, evidence also shows that some OASIs are missed or misclassified at the time of birth, meaning the true burden of injury may not always be reflected in routinely recorded figures.

The gap between what is recorded and what many women and birthing people experience is reflected in the costs of OASI‑related litigation. In a recent thematic review of claims in England, NHS Resolution identified 237 cases linked to OASI over a ten‑year period, with closed cases costing around £60 million once damages and associated expenses are included.

What the litigation tells us about OASI today

The OASI claims examined by NHS Resolution reveal a consistent pattern within NHS maternity services in England: when these tears are not recognised promptly, the delayed diagnosis has knock‑on effects for maternal outcomes and increases the likelihood of legal action. Here are the key findings. 

Missed tears and delayed diagnosis

In cases where damages were awarded, more than half of women and birthing people (58%) had a perineal tear that was initially graded as less severe than it really was. Many were later found to have sustained an OASI that had not been detected at the time of birth. 

The average delay from delivery to accurate diagnosis was approximately 294 days (close to ten months) with some women and birthing people waiting several years before the full extent of their injury was recognised.

Birth context 

Around six in ten had an instrumental delivery, most commonly with forceps. Episiotomy was performed in the majority of forceps births. Instrumental birth is often clinically necessary and can be life‑saving for mother or baby, but the claims data suggest that when forceps are used, the risk of severe perineal trauma increases.

The lasting toll

The symptoms described in the claims also underline the human cost of undiagnosed or poorly managed OASI. Faecal incontinence was the most frequently reported complaint, affecting roughly four in five women and birthing people in the cohort. Many also reported embarrassment, social withdrawal, strain on intimate relationships and difficulties returning to work or caring for their baby in the way they had hoped.

Priorities for safer maternity care 

The litigation picture makes it clear that while not all OASIs are preventable, earlier recognition and appropriate management may help reduce the risk of some of the longer-term consequences associated with missed injury. The report points towards several practical priorities for maternity services, all of which can help to reduce harm and future OASI‑related claims.

Safer assisted vaginal births 

Assisted vaginal births are a key point of risk for OASI, particularly when forceps are used. Regular, hands-on training in decision-making and instrumental technique can both reduce the likelihood and severity of OASI. 

Stronger supervision in complex deliveries

Many OASI claims involve births conducted by less experienced clinicians working with limited senior supervision. Ensuring visible consultant presence for complex or assisted births, alongside clear thresholds for escalation, makes it easier for teams to ask for help early. This support is particularly important when OASI risk is high, such as in rotational forceps deliveries.

Early diagnosis 

With missed or under‑graded tears a major driver of OASI claims, a consistent, structured perineal assessment after every vaginal birth is essential to detect OASI at the earliest opportunity. Research shows that digital rectal examination (DRE) can be unreliable, missing up to 80% of injuries. Instead, maternity teams should look to medical devices to support objective diagnosis. 

Conclusion

The OASI claims reviewed by NHS Resolution tell a consistent story: much of the litigation surrounding this injury is driven not by the tear itself, but by OASI that is missed or undergraded.

The findings reinforce the importance of giving clinicians the tools and confidence to identify OASI accurately at the earliest opportunity. Technologies such as ONIRY have the potential to complement clinical examination by providing an objective assessment at the bedside, supporting more informed decisions about appropriate care and repair.

ONIRY is a bedside probe device that uses AI-powered detection to accurately and objectively detect OASI in just 60 seconds. Oniry improves OASI detection by up to 200%, helping clinicians make confident decisions in the moments when it matters most.

To learn more about how ONIRY can support OASI detection in your service, visit the:

ONIRY product page