What are the causes of vulvar hematoma after vaginal delivery?

Causes of Vulvar Hematoma After Vaginal Delivery

Vulvar hematomas after vaginal delivery are primarily caused by trauma to the genital tract, with injury to blood vessels in the vulvovaginal area being the fundamental mechanism.

Primary Causes

1. Genital Tract Trauma

• Perineal lacerations: Spontaneous tears during delivery that damage blood vessels 1
• Episiotomy complications: Bleeding from vessels injured during episiotomy incisions 1
• Instrumental delivery: Use of forceps or vacuum extraction increasing risk of vessel injury 1
• Extension of incisions: When episiotomy incisions extend beyond intended margins 1

2. Vascular Factors

• Injury to branches of pudendal artery: Most common source of bleeding in vulvar hematomas 1
• Rupture of varicose veins: Pre-existing vulvar varicosities that rupture during delivery 1
• Vessel fragility: Increased vascularity of the perineum during pregnancy 2

3. Coagulation Disorders

• Inherited coagulopathies: Underlying bleeding disorders that manifest during delivery 1, 2
• Acquired coagulopathies: From conditions such as HELLP syndrome, severe pre-eclampsia, or amniotic fluid embolism 1
• Anticoagulant therapy: Women on therapeutic anticoagulation are at increased risk 1

Risk Factors

Maternal Factors

• Nulliparity: First-time mothers have higher risk of perineal trauma 1
• Maternal size: Disproportion between maternal pelvis and fetal size 1
• Pre-existing vulvar varicosities: Increased risk of vessel rupture 2

Delivery-Related Factors

• Precipitous delivery: Rapid expulsion causing uncontrolled stretching and tearing 1
• Prolonged second stage of labor: Increased pressure on perineal tissues 1
• Large fetal size: Macrosomia causing increased perineal stretching 1
• Operative vaginal delivery: Forceps or vacuum assistance 1

Pathophysiology

The mechanism of vulvar hematoma formation involves:

1. Initial vessel injury: Trauma to blood vessels during delivery 1
2. Bleeding into soft tissue spaces: Blood accumulates in the loose connective tissue of the vulva 1, 3
3. Hematoma expansion: Continued bleeding with potential tamponade effect 4
4. Anatomical considerations: The vulva's rich vascular supply and loose connective tissue allow for significant expansion of hematomas 1

Clinical Presentation

• Timing: Usually within 24 hours of delivery (primary postpartum hemorrhage) 1, 2
• Symptoms: Severe perineal pain, pressure sensation, urinary retention 4
• Signs: Unilateral vulvar swelling, discoloration, tenderness 5

Diagnostic Considerations

• Clinical examination: Visual inspection and palpation of the vulva 1
• Imaging: Enhanced CT scan may reveal active bleeding and extent of hematoma 3
• Differential diagnosis: Must distinguish from other causes of postpartum hemorrhage 1, 2

Prevention Strategies

• Careful perineal management: Controlled delivery of the fetal head 1
• Appropriate episiotomy technique: When indicated, proper angle and timing 1
• Management of third stage: Active management with uterotonics to reduce overall bleeding risk 1, 2
• Recognition of risk factors: Increased vigilance in high-risk cases 1

Understanding these causes is essential for prevention, early recognition, and appropriate management of vulvar hematomas after vaginal delivery, which can significantly reduce maternal morbidity.