A 28-year-old primigravida delivers a healthy 3.2 kg male infant vaginally after 8 hours of active labor. Two hours postpartum, she has vaginal bleeding of 800 mL with a boggy uterus on palpation and a fundus at the level of the umbilicus. What is the most common cause of postpartum hemorrhage in this scenario?

Explanation

## Most Common Cause of Postpartum Hemorrhage **Key Point:** Uterine atony accounts for 50–60% of all cases of postpartum hemorrhage (PPH), making it the single most common cause worldwide [cite:Williams Obstetrics 26e Ch 41]. ### Clinical Presentation of Uterine Atony The clinical vignette is classic for uterine atony: - **Boggy, soft uterus** on abdominal palpation (loss of muscle tone) - **Fundus remains high** (at or above umbilicus) despite delivery - **Brisk vaginal bleeding** in the immediate postpartum period (first 2–4 hours) - **Lochia is dark and excessive** ### Epidemiology & Risk Factors | Risk Factor | Mechanism | |---|---| | Prolonged labor | Uterine muscle fatigue | | Multiparity | Reduced myometrial contractility | | Polyhydramnios | Overdistension of uterus | | Macrosomia | Excessive uterine stretch | | Oxytocin use | Tachyphylaxis if prolonged | | General anesthesia | Myometrial depression | **High-Yield:** In this primigravida with a normal-sized infant and uncomplicated labor, the absence of predisposing factors makes uterine atony the default diagnosis when a boggy uterus and excessive bleeding are present. ### Differential Diagnosis: Why Other Causes Are Less Likely **Retained placental fragments** (15–25% of PPH): - Typically present with delayed bleeding (after 6–12 hours) or subinvolution - Uterus may be firm initially, then become boggy later - Less likely in the immediate 2-hour window with a clearly boggy fundus **Genital tract trauma** (15–25% of PPH): - Presents with brisk, bright-red bleeding from the vagina, perineum, or cervix - Uterus is typically **firm and well-contracted** - Requires direct visualization to diagnose - Not consistent with a boggy uterus **Coagulopathy** (5–10% of PPH): - Rare as a primary cause; usually secondary to massive transfusion or DIC - Does not explain a boggy uterus - Bleeding is diffuse (oozing from multiple sites) ### Management Approach 1. **Immediate uterine massage** to stimulate contraction 2. **Oxytocin 10 IU IV** (or IM if IV unavailable) 3. **Empty bladder** (distended bladder impairs uterine contraction) 4. **IV fluids and blood products** as needed 5. **Ergot alkaloids** (methylergonovine) if oxytocin fails 6. **Prostaglandins** (carboprost, misoprostol) for refractory cases **Clinical Pearl:** The combination of a **boggy uterus + excessive bleeding + normal delivery** is pathognomonic for uterine atony. This is the most frequently tested scenario in NEET PG PPH questions.