A 32-year-old G3P2 woman undergoes emergency lower-segment cesarean section (LSCS) for failure to progress at 8 cm dilation after 16 hours of labor. Intraoperatively, the lower uterine segment is thin and edematous. The baby (3.8 kg) is delivered without difficulty. During closure of the uterine incision, the surgeon notices that the myometrium is difficult to approximate and bleeding from the incision edges is brisk despite adequate hemostasis. Estimated blood loss at surgery is 1200 mL. In the recovery room, lochia is moderate but the uterus remains soft. Hemoglobin drops from 10.5 g/dL preoperatively to 8.1 g/dL postoperatively. What is the most likely cause of excessive bleeding in this case?

Explanation

## Diagnosis: Uterine Atony Secondary to Prolonged Labor **Key Point:** Prolonged labor causes myometrial exhaustion, leading to impaired contractility and increased risk of postpartum hemorrhage even after cesarean delivery. This is one of the most important modifiable risk factors for PPH in operative deliveries. ### Why Atony in This Case? | Clinical Feature | Interpretation | |------------------|----------------| | **16 hours of labor** | Prolonged first/second stage → myometrial fatigue | | **Soft uterus postop** | Direct evidence of inadequate contractility | | **Brisk bleeding from incision edges** | Failure of myometrial contraction to compress vessels | | **Moderate lochia** | Ongoing ooze, not a single source bleed | | **Thin, edematous lower segment** | Overworked myometrium; poor contractile reserve | | **Large baby (3.8 kg)** | Increased uterine distension → atony risk | | **Hemoglobin drop 2.4 g/dL** | Significant but manageable with transfusion | **High-Yield:** The combination of prolonged labor + soft uterus + diffuse oozing from the incision = atony. This is a **preventable** cause of PPH if labor is managed appropriately (augmentation, timely intervention). ### Pathophysiology of Labor-Induced Atony 1. **Prolonged myometrial contraction** → depletion of ATP and glycogen stores 2. **Accumulation of lactate and metabolic byproducts** → impaired calcium handling 3. **Loss of contractile protein function** → inability to generate adequate tension 4. **Edema and inflammation** → further impairment of myometrial function **Clinical Pearl:** Cesarean section does NOT prevent atony if the underlying cause (prolonged labor) has already exhausted the myometrium. The uterus is already "tired" before surgery begins. ### Risk Factors for Atony — **TIRED Mnemonic** **T** – Too much (polyhydramnios, macrosomia, multiparity) **I** – Infection (chorioamnionitis) **R** – Rapid or **prolonged** labor (exhaustion) **E** – Exhausted uterus (multiparity, previous atony) **D** – Drugs (magnesium sulfate, nifedipine, anesthetics) This patient has **R** (prolonged labor) and **T** (large baby, multiparity). ### Differential Diagnosis in Operative PPH ```mermaid flowchart TD A[Excessive bleeding during/after LSCS]:::outcome --> B{Uterus firm or soft?}:::decision B -->|Soft| C[Atony]:::outcome B -->|Firm| D{Bleeding source?}:::decision D -->|Incision edges| E[Inadequate hemostasis or coagulopathy]:::outcome D -->|Placental bed| F[Placental invasion or retained fragments]:::outcome D -->|Lower abdomen| G[Bladder or vessel injury]:::outcome C --> H[Oxytocin, ergot, misoprostol, massage]:::action E --> I[Check PT/INR, platelet count]:::action F --> J[Inspect placenta, consider imaging]:::action G --> K[Surgical exploration]:::action ``` ### Management of Atony in Cesarean Section **Immediate steps:** 1. **Uterine massage** through the abdominal incision 2. **Oxytocin 10 IU IV/IM** (or 20 IU in 500 mL NS infusion) 3. **Ergot alkaloid** (methylergonovine 0.2 mg IM) if no hypertension 4. **Misoprostol 800 mcg PR** if available 5. **Ensure adequate anesthesia** (atony worsens with inadequate pain control) **Tip:** Oxytocin should be given **before** closing the uterus in high-risk cases (prolonged labor, macrosomia). This is standard practice in many centers. **Warning:** Do NOT assume the bleeding is from the incision itself. Always palpate the uterus to assess tone before attributing PPH to surgical hemostasis issues.