Anticoagulants in pregnancy: fetal effects.

Anticoagulants are used during pregnancy to prevent venous thrombo-embolism in highrisk patients, to prevent systemic embolism in patients with prosthetic heart valves or native valvular heart disease, and to treat patients with acute venous thrombo-embolism. Neither unfractionated nor low-molecular-weight heparin cross the placenta and both appear to be safe for the fetus. Oral anticoagulants do cross the placenta and they have been associated with the development of warfarin embryopathy, central nervous system anomalies, and fetal haemorrhage. The true incidence of these events is not known. Both heparin and oral anticoagulants can be safely administered to nursing mothers.