A 26 year old pregnant woman has been detected to have murmur in mitral area. Echocardiography reveals mitral valve orifice to be 0.8 cm2. The cause of her murmur is -

• A. Mild mitral stenosis
• B. Severe mitral stenosis
• C. Functional murmur
• D. Transmitted murmur from the congenital heart disease of the fetus