Pulmonary Embolism (PE): Although not the most common, it's a leading concern due to the hypercoagulable state of pregnancy, which increases the risk of thromboembolic events. Symptoms of SOB, especially if acute in onset, warrant consideration of PE.

Asthma: Pre-existing asthma can worsen during pregnancy due to various physiological changes, including increased blood volume and airway hyperresponsiveness.
Pregnancy-Induced Hypertension: Can lead to pulmonary edema, causing shortness of breath.
Anemia: Common in pregnancy due to increased blood volume and demand for iron, leading to reduced oxygen-carrying capacity and potential shortness of breath.
Gastroesophageal Reflux Disease (GERD): Symptoms can worsen during pregnancy, potentially causing respiratory discomfort or SOB.

Pulmonary Embolism (already mentioned but critical to reiterate): Due to its high mortality rate if not promptly treated.
Amniotic Fluid Embolism: A rare but catastrophic event that can occur during pregnancy, characterized by sudden onset of SOB, hypotension, and potentially cardiac arrest.
Placenta Previa or Abruption: Although primarily associated with bleeding, these conditions can lead to maternal hypovolemia and subsequent respiratory distress.
Cardiac Conditions (e.g., Peripartum Cardiomyopathy): New onset of cardiac dysfunction can present with SOB and is critical to diagnose and manage to prevent maternal and fetal morbidity.

Idiopathic Pulmonary Arterial Hypertension (IPAH): Although rare, it can present during pregnancy with symptoms of SOB and has significant implications for maternal and fetal health.
Lymphangioleiomyomatosis (LAM): A rare lung disease that can cause SOB, more commonly diagnosed in women of childbearing age.
Cystic Fibrosis: If not previously diagnosed, could present with respiratory symptoms during pregnancy due to increased respiratory demand and potential exacerbations.