Exam & testing. Best diagnosed by a combination of history of symptoms, physical exam findings and testing (which may include lab test, chest x-ray with lead protection and ultrasound of heart).
Rare condition. Pulmonary edema is rare in healthy young women without pregnancy complications. However, when a woman is at risk, regularly watching her intake of fluids and output, listening to her lungs and asking questions and paying attention to what she says can raise suspicion of the development of edema or fluid in the lungs. An xray, with the abdomen shielded, can give additional information if needed.