perineal trauma

Perineal tears are the most common maternal obstetric injuries

Tear classification

First degree	Injury to perineal skin only
Second degree	Injury involving perineal skin and muscle but not anal sphincters
Third degree	Injury involving anal sphincters
3A	<50% external anal sphincter
3B	>50% external anal sphincter
3C	Involvement of both external and internal anal sphincter
Fourth degree	Disruption of anal epithelium/mucosa

An episiotomy is performed in the second stage, usually when the perineum is being stretched and it is deemed necessary to prevent severe tearing
A mediolateral episiotomy is usually recommended