Table 5: Classification of perineal injuries.

Classified by severity of wound and tissue damage

1^st degree tear, involves perineal skin layer only.

2^nd degree tear, involves posterior vaginal wall, subcutaneous fat, perineal skin layer, superficial muscles (bulbocavernosus and transverse perinei) and deep muscle (pubococcugeus).

Episiotomy involves the same structures as for 2^nd degree tears.

3^rd degree tears, involve the same structures as for 2^nd degree tears and in addition, the anal sphincter.

3^rd degree tears are classified by injuries to the external anal sphincter (EAS), internal anal sphincter (IAS) and anal epithelium.

3a < 50% of external anal sphincter (EAS) thickness torn.

3b > 50% of EAS thickness torn.

3c Internal anal sphincter (IAS) torn.

A 4^th Degree tear, involves the anal sphincter complex (EAS and IAS) and anal epithelium.