Grade I: First-Degree Perineal Tear
Shallow injury to skin and mucosa only, usually healing fast.
- ~2 mm: Depth (skin/mucosa)
- ~14 days: Healing time (typical)
- Often none: Suturing (or minimal)
- 1–2%: Incontinence risk (low)
What defines Grade I
Superficial tear of fourchette, perineal skin, vaginal mucosa only.
Grade II: Second-Degree Tear
Extends into perineal muscles but the anal sphincter stays intact.
- ~8 mm: Depth (muscle layer)
- ~21 days: Healing time (typical)
- Layered repair: Suturing (usually needed)
- 5–10%: Incontinence risk (moderate)
What defines Grade II
Most common obstetric tear; includes most episiotomies.
Grade III: Anal Sphincter Injury
Obstetric anal sphincter injury (OASIS) affecting continence muscles.
- ~15 mm: Depth (sphincter complex)
- ~35 days: Healing time (typical)
- 3a–3c: Subtypes (% torn)
- 20–30%: Incontinence risk (elevated)
What defines Grade III
Partial or complete tear of external/internal anal sphincter.
Grade IV: Full-Thickness Rectal Injury
Most severe tear, breaching the rectal mucosa itself.
- ~25 mm: Depth (full thickness)
- ~56 days: Healing time (typical)
- OR repair: Repair (specialist required)
- 30–60%: Incontinence risk (high)
What defines Grade IV
Tear continuous through sphincter into rectal lumen mucosa.
Healing Timelines Across Severity Grades
Recovery duration scales strongly with initial tissue damage depth.
- 14 d: Grade I (healing window)
- 21 d: Grade II (healing window)
- 35 d: Grade III (healing window)
- 56 d: Grade IV (healing window)
Comparing recovery curves
Higher grades need longer tissue remodeling and closer monitoring.
Severe tears warrant structured follow-up and pelvic floor rehab.