Table 1 ICD-10 classification of perineal injuries

First

Injury to vaginal mucosa or perineal skin only

Second

Injury to vaginal mucosa or perineal skin and superficial perineal muscles

Third

Injury to anal sphincter muscles and subdivided into

 3A

< 50% of external anal sphincter muscles is injured

 3B

> 50% of external anal sphincter muscle is injured

 3C

External and internal anal sphincter muscles are injured

Fourth

Injury involving external and internal anal sphincter muscles and anal epithelium