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.
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Read the corresponding patient information on this topic which has also been published.