The reported rate of OASIS (in singleton, term, cephalic, vaginal first births) in England has tripled from 1.8% to 5.9% from 2000 to 2012. The overall incidence in the UK is 2.9% (range 0–8%), with an incidence of 6.1% in primiparae compared with 1.7% in multiparae. With increased awareness and training, there appears to be an increase in the detection of anal sphincter injuries. A trend towards an increasing incidence of third- or fourth-degree perineal tears does not necessarily indicate poor quality care. It may indicate, at least in the short term, an improved quality of care through better detection and reporting.
Obstetricians who are appropriately trained are more likely to provide a consistent, high standard of anal sphincter repair and contribute to reducing the extent of morbidity and litigation associated with anal sphincter injury.
This guideline developed as part of the regular programme of Green-top Guidelines, as outlined in our document Developing a Green-top Guideline: Guidance for developers, and prior to the emergence of COVID-19.
This is the third edition of this guideline; the fourth edition is currently in development.
Developer declaration of interests
Dr RJ Fernando: Mr Fernando has received speaker fees and travel grants from Astellas, AMS, Pfizer and Laborie unrelated to this topic.
Mr AH Sultan: Mr Sultan has previously been a speaker for Astellas and Pfizer. He is the co-director of the Croydon perineal and anal sphincter trauma courses.
Professor RM Freeman: Professor Freeman has received speaker fees from Astellas and Pfizer and has been on a European advisory board for Astellas. He has a patent/patents pending on Episcissors-60 as an inventor and is IUGA President.
Dr AA Williams: Dr Williams is on the Astellas and Femeda medical advisory board and has received sponsorship/honorarium for speaker meetings from Pfizer and Astellas.
Dr EJ Adams: None declared.