Hazards of oral anticoagulants during pregnancy.

Prenatal exposure to oral anticoagulants during pregnancy may result in defective fetal development or life-threatening hemorrhage. Fetal exposure during the first eight weeks of pregnancy may cause abnormal development of the facial structures, hypoplastic digits, strippled epiphyses, and mental retardation. Midtrimester exposure may result in optic atrophy, faulty brain growth, and developmental retardation. Third-trimester exposure may produce fetal anticoagulation, predisposing the infant to life-threatening hemorrhage in the perinatal period. Anticoagulation with heparin sodium does not provide a clearly safe alternative, since this therapy has been associated with excessive fetal loss.