A delivery with forceps from "Die Einfuhrung des rechten Loffels. Scanzoni 1855. A delivery with forceps from "Die Einfuhrung des rechten Loffels. Scanzoni 1855.

Risk factors to grade 3 and 4 tears:

 
First vaginal delivery

Instrumental delivery (vacuum, forceps)

Big baby, over 4 kg

Long lasting delivery

Oxytocin augmentation 

Earlier grade 3 or 4 tear

Mathernal age, age over 35 years increases the risk sligthly

Epidural analgesia

Poor perineal support

Incorrect episiotomy