[Anticoagulation in patients with heart valve replacement in pregnancy].

Oral anticoagulants are the drugs of first choice for an effective anticoagulation after mechanical and biological heart valve replacement. Patients with mechanical heart valves are anticoagulated life long, whereas biological prostheses are anticoagulated for 3 months postoperatively in the case of sinus rhythm. Life-long anticoagulation in biological heart valve replacement is indicated if atrial fibrillation or dilatation of the left atrium or peripheral arterial embolism are present. During pregnancy oral anticoagulants are contraindicated in the first trimester. Heparins are effective alternatives for anticoagulation during this period. However, the dose of heparin has to be adjusted according to the activated partial thromboplastin time, which should be 1.5-fold prolonged. Low-molecular-weight heparins may be an alternative due to improved pharmacokinetics. Neither unfractionated nor low-molecular-weight heparin cross the placenta.