A 28-year-old primigravida delivers a healthy 3.2 kg male infant vaginally after a 12-hour labor. The third stage of labor is managed with oxytocin 10 IU IM. At 45 minutes postpartum, the fundus is at the level of the umbilicus and boggy. Vaginal bleeding is brisk, with an estimated blood loss of 800 mL. Vital signs: BP 100/62 mmHg, HR 108/min, RR 20/min. Hemoglobin is 9.2 g/dL (predelivery 11.8 g/dL). The placenta has been delivered completely and intact. What is the most likely diagnosis and immediate next step?

Explanation

## Clinical Diagnosis: Uterine Atony **Key Point:** Uterine atony is the most common cause of primary postpartum hemorrhage (PPH), accounting for 80–90% of cases. It occurs when the myometrium fails to contract adequately after delivery, preventing compression of spiral arteries. ### Clinical Features Supporting Atony | Feature | Finding in This Case | | --- | --- | | Timing | 45 minutes postpartum (within primary PPH window: 0–24 hrs) | | Fundal consistency | Boggy, soft uterus (hallmark of atony) | | Fundal height | At umbilicus (indicates inadequate contraction) | | Blood loss | 800 mL (exceeds normal 300–500 mL) | | Placenta | Delivered completely and intact (rules out retention) | | Hemodynamic status | Mild tachycardia and borderline BP (compensated hemorrhage) | ### Pathophysiology In a contracted uterus, the myometrial fibers compress the spiral arteries, creating a physiologic "living ligature." Atony abolishes this mechanism, leading to continued bleeding from the placental bed. **High-Yield:** Risk factors for atony include: - Multiparity - Prolonged or augmented labor - Fetal macrosomia - Polyhydramnios - Uterine overdistension ### Immediate Management Algorithm ```mermaid flowchart TD A[Suspected Uterine Atony]:::outcome --> B[Uterine Massage]:::action B --> C[Oxytocin 10 IU IV/IM]:::action C --> D{Response?}:::decision D -->|Bleeding stops| E[Continue oxytocin infusion]:::action D -->|Bleeding persists| F[Add Ergot Alkaloid or Misoprostol]:::action F --> G{Response?}:::decision G -->|Yes| H[Continue medical management]:::action G -->|No| I[Consider surgical intervention]:::urgent ``` ### Immediate Next Steps (in order) 1. **Uterine massage**: Firm, bimanual compression of the fundus to stimulate contraction 2. **Oxytocin**: Already given IM; may need IV infusion (10 IU in 500 mL saline at 40 mIU/min) 3. **Ergot alkaloid** (methylergonovine 0.2 mg IM/IV): If oxytocin alone fails (contraindicated in hypertension) 4. **Misoprostol** (600–1000 μg PR): Alternative if ergot unavailable or contraindicated 5. **IV access & fluid resuscitation**: Two large-bore cannulae, crystalloid, and blood products as needed **Clinical Pearl:** The "4 T's" mnemonic for PPH causes — **Tone** (atony), **Tissue** (retained placenta/clots), **Trauma** (lacerations), **Thrombin** (coagulopathy) — helps systematically rule out other etiologies. This case fits "Tone" perfectly. **Warning:** Do NOT use ergot alkaloids in patients with hypertension or pre-eclampsia, as they cause sustained uterine contraction and may precipitate hypertensive crisis. [cite:Williams Obstetrics 26e Ch 41]