Mechanical heart valve thrombosis during pregnancy is a challenging condition. We present a pregnant patient with stuck mechanical mitral valve. During the 36th week of pregnancy, she was admitted to our emergency clinic because of aggravated dyspnea, tachypnea, and cyanosis. Echocardiography revealed stuck mechanical valve in mitral position and she was diagnosed with acute left ventricular heart failure due to mechanical valve thrombosis. Reoperative mitral valve replacement was performed in emergency conditions immediately following Cesarean section. She and her baby were discharged 11 days after surgery without complications.