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Project background

Background and history of the OASI Care Bundle project

What is OASI?

An OASI is an obstetric anal sphincter injury which can occur during vaginal birth, sometimes referred to as severe perineal tearing. The long-term consequences of OASI include anal incontinence and painful sexual intercourse (dyspareunia) which can result in significant emotional and medical impact on women.


Population-based studies from Scandinavian countries and Canada identified an increase in the occurrence of OASI. Between 2000 and 2011, OASI rates were also shown to have increased in England.

This trend towards an increasing incidence of third or fourth degree perineal tears did not necessarily indicate poor-quality care.

Tearing is a complex issue which could be influenced by a range of factors including; advanced maternal age at first birth, larger maternal BMI and birth weight of the baby, instrumental birth and better detection and reporting.

However, as OASI can dramatically impact the short and long-term health of women influencing decisions about future births, prevention and management of OASI is a priority.

Experiences in some maternity units in England highlighted that some of the underlying problems related to this rise in OASI include:

  • Inconsistencies in approaches to preventing OASIs
  • Inconsistencies in training and skills
  • Lack of awareness of risk factors and long-term impact of OASIs
  • Variation in practice between health professionals

In light of this, the OASI Care Bundle team developed and piloted an intervention package, including a care bundle and guide, a multidisciplinary skills development module for health care professionals, and campaign materials designed to raise awareness among clinicians and women).

The OASI Care Bundle Project received funding from the Health Foundation Scaling Up Programme to implement this intervention in 16 maternity units across England, Scotland and Wales from 2016 to 2018.

Aims of the programme

The initial aims of the OASI Care Bundle project were:

  • To investigate and identify patterns of care, morbidity and outcomes related to women who suffered an OASI in Great Britain
  • To raise awareness about the incidence of OASI among all health professionals involved in maternity care
  • To review the literature on clinical interventions for the prevention of OASI
  • To produce an evidence-based care bundle to support clinical practice
  • To pilot the care bundle in a sample of units

This project focused on OASI resulting from labour and vaginal birth. The project excluded the management and prevention of OASI resulting from gynaecological/urological procedures. It also excluded considerations on repair techniques and related co-morbidities. 

The OASI Care Bundle

As part of the programme, a multidisciplinary team of national UK experts, supported by national professional organisations, developed a ‘care bundle’, which is a set of interventions likely to improve outcomes when implemented together. The elements of the care bundle were selected based on recommendations from existing UK guidelines.

The elements of the OASI bundle included:

  1. Informing women about OASI and identifying what can be done to minimise her risk
  2. Performing an episiotomy (a cut in the perineum to assist birth and prevent tears) when required
  3. Using the hands to support the perineum at the time of birth, and
  4. A thorough rectal examination after birth to detect tears, not all of which will be immediately obvious.

All elements of the care bundle are underpinned by good communication with the woman before, during and after birth.

We developed and piloted an intervention package which brought together the care bundle, a skills development module for clinicians and campaign materials to raise awareness among clinicians and women.


16 maternity units in England, Scotland and Wales were recruited to the study, with both a midwifery and an obstetric champion volunteering to lead the programme from within each hospital. Support from local clinical champions, opinion leaders and professional organisations, as well as patient and public involvement and continuous monitoring and feedback, helped ensure that the interventions were acceptable to women and health care professionals.

The programme ran for 2.5 years. The evaluation of the programme included an analysis of the impact of the OASI Care Bundle on clinical practice and outcomes, and the acceptability of the care bundle to women and clinicians. The results were published in August 2020 and are available to download below.

This project focused on OASI resulting from labour and vaginal birth. The project excluded the management and prevention of OASI resulting from gynaecological/urological procedures. It also excluded considerations on repair techniques and related co-morbidities.

Read the study protocol here


The programme included the following activities:

Outputs of the OASI project

Analysis of secondary care data

Evaluation papers

Contact us

For more information about the OASI Care Bundle, please  or call +44 20 7772 6285.