1st degree: Graze (dermis layer affected, muscle layer unaffected)
2nd degree: +Mucosa and muscle layer affected
3rd degree: +External anal sphincter
3A <50% External anal sphincter thickness torn
3B >50% External anal sphincter thickness torn
3C External anal sphincter + Internal anal sphincter torn
4th degree: Rectal mucosa affected
Repair: 1st degree tears rarely need suturing unless blood loss is marked. If 4th degree tear, repair rectal mucosa first, followed by vaginal mucosa. Always suture from above the tear's apex.
2nd degree: +Mucosa and muscle layer affected
3rd degree: +External anal sphincter
3A <50% External anal sphincter thickness torn
3B >50% External anal sphincter thickness torn
3C External anal sphincter + Internal anal sphincter torn
4th degree: Rectal mucosa affected
Repair: 1st degree tears rarely need suturing unless blood loss is marked. If 4th degree tear, repair rectal mucosa first, followed by vaginal mucosa. Always suture from above the tear's apex.