Third and Fourth Degree Perineal Tear in Four-Year Period at Sestre Milosrdnice University Hospital Center, Zagreb, Croatia.

Objectives: Obstetric anal sphincter injury (OASIS) includes the third and fourth degree of perineal injury. The risk for OASIS is about 1% of all vaginal deliveries. If not recognised and treated properly, obstetric anal sphincter injury can have serious consequences for reproductive age woman.