A 28-year-old primigravida delivers a healthy 3.2 kg male infant vaginally after 8 hours of labor. The third stage of labor is managed with oxytocin 10 IU IM. At 45 minutes postpartum, the patient complains of severe lower abdominal pain and vaginal bleeding that soaks 2 pads in 10 minutes. On examination, the uterus is soft, boggy, and enlarged to 3 fingerbreadths above the umbilicus. Lochia is dark red with clots. Vital signs: BP 100/62 mmHg, HR 110/min, RR 20/min. Hemoglobin is 9.2 g/dL (pre-delivery 11.8 g/dL). What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Uterine Atony with Postpartum Hemorrhage ### Key Clinical Features **Key Point:** Uterine atony is the most common cause of postpartum hemorrhage (PPH), accounting for 70–80% of cases [cite:Williams Obstetrics 26e Ch 41]. The clinical presentation is classic for uterine atony: - **Soft, boggy, enlarged uterus** — hallmark finding indicating loss of myometrial contractility - **Excessive vaginal bleeding** (2 pads in 10 minutes) in the immediate postpartum period - **Dark red lochia with clots** — indicates ongoing bleeding from placental bed - **Hemodynamic changes** — tachycardia (110/min) and borderline hypotension (100/62) reflect acute blood loss - **Hemoglobin drop** of 2.6 g/dL within 45 minutes is significant ### Pathophysiology of Uterine Atony 1. Loss of myometrial contraction → placental vessels remain patent 2. Continued bleeding from spiral arteries at placental bed 3. Uterus fails to compress bleeding vessels ("living ligature" mechanism absent) ### Risk Factors Present - Primigravida (increased uterine distension) - Prolonged labor (myometrial fatigue) ### Management Algorithm ```mermaid flowchart TD A[Uterine atony diagnosed]:::outcome --> B[Empty bladder]:::action B --> C[Uterine massage]:::action C --> D[IV oxytocin 10 IU/500 mL saline]:::action D --> E{Bleeding controlled?}:::decision E -->|Yes| F[Continue oxytocin infusion]:::action E -->|No| G[Add ergot alkaloid or misoprostol]:::action G --> H{Bleeding controlled?}:::decision H -->|Yes| F H -->|No| I[Prepare for surgical intervention]:::urgent I --> J[Uterine compression sutures or hysterectomy]:::action ``` ### High-Yield Differentiating Features | Feature | Uterine Atony | Placental Abruption | Uterine Rupture | Cervical Laceration | |---------|--------------|-------------------|-----------------|--------------------| | **Uterine tone** | Soft, boggy | Firm, tender | Hard, rigid | Normal | | **Bleeding onset** | Immediate (3rd stage) | May be concealed | Catastrophic | Immediate but controlled | | **Abdominal pain** | Mild cramping | Severe, constant | Severe, shock | Minimal | | **Hemodynamic status** | Gradual deterioration | Rapid shock | Rapid shock | Stable initially | | **Lochia character** | Dark, clotty | Dark, clotty | Bloody, no clots | Bright red | **Clinical Pearl:** The **soft, boggy uterus** is the single most important diagnostic finding for uterine atony. Always palpate the uterus first in any PPH case. **High-Yield:** Uterine massage + oxytocin control 80% of atony cases; ergot alkaloids (methylergonovine) are added if oxytocin fails.