A 27-year old pregnant woman presented in our emergency department with syncope, dyspnea and complaints about an overall impairment. She had received aortic alloplastic heart valve replacement due to a congenital, valvular stenosis in 1993. We diagnosed a prosthetic heart valve thrombosis associated with cardiac decompensation. Due to tachycardia and critical hypotension we decided to perform fibrinolytic therapy with tenecteplase. After fibrinolysis both prosthetic heart valve leaflets were separating in normal and regular function. The patient was initially anticoagulated with low molecular weight heparin, which was switched during the hospital stay to unfractionated heparin. Later oral anticoagulation with phenprocoumon was initiated. At 36 weeks of gestation an uneventful elective abdominal caesarean section was performed. The mother and the newborn were in healthy condition. Hypercoaguability in pregnancy is a serious problem, especially for patients who already have an existing indication for therapeutic anticoagulation. Fibrinolysis should definitely be considered an option during pregnancy in critical and life-threatening situations.