A 32-year-old multiparous woman at term undergoes operative vaginal delivery with vacuum extraction for prolonged second stage. The procedure is unsuccessful after three pulls, and the cup detaches from the fetal head twice. Which is the most common site of scalp trauma following failed vacuum extraction?

Explanation

## Most Common Site of Scalp Trauma After Vacuum Extraction **Key Point:** Cephalohematoma (a subperiosteal collection of blood) over the parietal bone is the most common scalp injury following vacuum extraction, particularly when the procedure is prolonged or unsuccessful. It occurs in 5–20% of vacuum deliveries and up to 40% of failed vacuum extractions. ### Classification and Sites of Vacuum-Related Scalp Injuries | Injury Type | Location | Frequency | Mechanism | Clinical Significance | |---|---|---|---|---| | **Cephalohematoma** | Parietal (most common) | 5–20% (40% if failed) | Subperiosteal bleeding | Usually benign; resolves in weeks | | **Caput succedaneum** | Occiput/presenting part | 10–15% | Subcutaneous edema | Transient; resolves in 24–48 hrs | | **Subgaleal hemorrhage** | Beneath galea aponeurosis | 0.4–1.5% | Deeper bleeding | **Serious; can cause hypovolemia** | | **Intracranial hemorrhage** | Subdural/epidural | <0.1% | Severe trauma | Rare; requires imaging | **High-Yield:** The parietal bone is the most common site of cephalohematoma because: 1. It is the widest part of the fetal skull and bears the most traction force during vacuum extraction. 2. The periosteum over the parietal bone is more easily separated from bone by negative pressure. 3. The parietal region is the typical point of application for vacuum cups (flexion point). ### Why Each Injury Occurs ```mermaid flowchart TD A[Vacuum Extraction Applied]:::action --> B{Traction Force & Duration}:::decision B -->|Mild, brief| C[Caput succedaneum]:::outcome C --> C1[Subcutaneous edema<br/>Occiput/presenting part] B -->|Moderate, repeated| D[Cephalohematoma]:::outcome D --> D1[Subperiosteal bleeding<br/>Parietal bone most common] B -->|Severe, prolonged<br/>or multiple detachments| E[Subgaleal hemorrhage]:::urgent E --> E1[Deeper bleeding<br/>Risk of hypovolemia] B -->|Extreme trauma| F[Intracranial hemorrhage]:::urgent F --> F1[Subdural/epidural<br/>Rare] ``` **Clinical Pearl:** Cephalohematoma typically appears 12–24 hours after delivery (unlike caput succedaneum, which is present at birth). It is usually self-limited and does not require intervention unless there is evidence of ongoing bleeding or infection. **Warning:** Do not confuse caput succedaneum (transient, subcutaneous edema) with cephalohematoma (subperiosteal collection). Caput crosses suture lines; cephalohematoma does not. ### Risk Factors for Severe Scalp Injury - Multiple cup detachments (as in this case: "cup detaches twice") - Prolonged traction (>3 contractions per pull) - High station at application (>+2) - Inexperienced operator - Failed vacuum extraction requiring cesarean section **Mnemonic: CUPS** — **C**ephalohematoma (parietal, subperiosteal), **U**nsuccessful pulls (risk factor), **P**arietal bone (most common site), **S**ubgaleal (serious complication).