A 22-year-old woman with an uncomplicated pregnancy develops sudden dyspnea with cyanosis and hypotension intrapartum during routine vaginal delivery of a term infant. She has a generalized seizure and becomes comatose. Her condition does not improve over the next 2 days. Which of the following findings is most likely to be present in her peripheral pulmonary arteries?

**Core Concept**
The patient's presentation suggests a catastrophic event leading to acute right heart failure, likely due to a pulmonary embolism (PE) or amniotic fluid embolism (AFE). Amniotic fluid embolism is a rare but life-threatening condition that occurs when amniotic fluid enters the maternal circulation, triggering a severe inflammatory response and coagulopathy.

**Why the Correct Answer is Right**
The patient's symptoms, including sudden dyspnea, cyanosis, hypotension, seizure, and coma, are consistent with a massive pulmonary embolism or amniotic fluid embolism. In the case of AFE, the amniotic fluid would likely be present in the peripheral pulmonary arteries, causing a severe inflammatory response and leading to the patient's catastrophic clinical course. This condition is often associated with significant pulmonary hypertension and right ventricular failure.

**Why Each Wrong Option is Incorrect**
* **Option A:** Atelectasis is a condition characterized by the collapse of lung tissue, which may occur in the setting of a PE, but it would not be the most likely finding in the peripheral pulmonary arteries in this scenario.
* **Option B:** Pulmonary edema is a common finding in heart failure, but it is not the most specific finding associated with AFE.
* **Option C:** Pulmonary infarction may occur in the setting of a PE, but it is not the most likely finding in the peripheral pulmonary arteries in this scenario.

**Clinical Pearl / High-Yield Fact**
Amniotic fluid embolism is a rare but devastating condition that can occur in the setting of a vaginal delivery, particularly if there has been a rupture of membranes or a prolonged labor. It is essential for obstetricians and anesthesiologists to be aware of the risk factors and clinical presentation of AFE to make a timely diagnosis and provide appropriate treatment.

**Correct Answer: D.**

✓ Correct Answer: B. Amniotic fluid