A 28-year-old primigravida delivers a healthy male infant vaginally after a 6-hour second stage. The third stage lasts 15 minutes with minimal bleeding. However, 2 hours postpartum, she develops brisk vaginal bleeding and becomes hemodynamically unstable. On examination, the uterus is soft and boggy. What is the most common cause of her postpartum hemorrhage?

Explanation

## Most Common Cause of Postpartum Hemorrhage **Key Point:** Uterine atony accounts for 50–60% of all cases of postpartum hemorrhage, making it the leading cause globally and in India. ### Pathophysiology of Uterine Atony Uterine atony occurs when the myometrium fails to contract adequately after delivery, preventing compression of the spiral arteries in the placental bed. This results in: 1. Failure of physiologic hemostasis at the placental site 2. Continued bleeding from open venous sinuses 3. Rapid blood loss if not promptly managed ### Clinical Recognition | Feature | Uterine Atony | Other Causes | |---------|---------------|---------------| | **Uterine consistency** | Soft, boggy, enlarged | Firm or normal size | | **Bleeding onset** | Often delayed (1–4 hours) | Variable timing | | **Fundal height** | Above umbilicus | Normal or below | | **Response to oxytocin** | Rapid improvement | May not respond | **Clinical Pearl:** A soft, boggy uterus with brisk bleeding in the early postpartum period is pathognomonic for atony. The clinical vignette describes exactly this scenario—delayed bleeding (2 hours postpartum) with a boggy uterus. ### Risk Factors for Uterine Atony - Prolonged labor - Rapid labor - High parity - Polyhydramnios - Fetal macrosomia - Placental abnormalities (previa, abruption) - General anesthesia - Magnesium sulfate use - Uterine overdistension **High-Yield:** Uterine atony is the ONLY cause of PPH that responds dramatically to uterotonic agents (oxytocin, ergot alkaloids, misoprostol). This therapeutic response is both diagnostic and confirmatory. ### Why This Case Is Uterine Atony 1. **Timing:** Bleeding started 2 hours after delivery—classic for atony 2. **Uterine findings:** Soft and boggy—hallmark of atony 3. **Hemodynamic instability:** Indicates significant ongoing bleeding 4. **Normal third stage:** Rules out retained placenta as primary cause **Mnemonic: ATONY** — **A**bsent contraction, **T**iming (delayed), **O**pen vessels, **N**eed uterotonics, **Y**ield to oxytocin [cite:Williams Obstetrics 26e Ch 41]