Why Is It More Difficult to Detect Pulmonary Embolism (PE)

Why is it more difficult to detect pulmonary embolism (PE) among pregnant women?

A) Because the normal physiological change of a pregnant woman may mask the key sign of PE
B) Because there are no evident signs and symptoms manifested in patients with pulmonary embolism
C) Because signs and symptoms develop during the late stage of PE and treatment is no longer beneficial
D) Because the signs and symptoms of PE are so subtle that it does not appear to be a concern for a pregnant woman