As the teratogenic effects of warfarin are well known, the medication is rarely prescribed to pregnant women. However, for some patients, the risks associated with discontinuing warfarin use may outweigh the risk of embryopathy. Patients with prosthetic heart valves carry a particularly high risk of thrombus formation due to the inorganic surface and turbulent blood flow generated by a mechanical prosthesis. The risk of blood clotting is further increased by generalized hypercoagulability as concentrations of clotting factors rise during pregnancy. This increased chance of blood clots leads to an increased risk of potentially fatal pulmonary or systemic emboli cutting off blood flow and oxygen to critical organs. Thus, some patients may continue taking warfarin throughout the pregnancy despite the risks to the developing child. Mechanism
Warfarins ability to cause fetal warfarin syndrome in utero stems from its ability to limit vitamin K activation. Warfarin binds to and blocks the enzyme Vitamin K epoxide reductase which is usually responsible for activating vitamin K during vitamin K recycling. Vitamin K, once activated, is able to add a carboxylic acid group to glutamate residues of certain proteins which assists in correct protein folding. Without active vitamin K, a fetus exposed to warfarin is unable to produce large quantities of clotting and bone growth factors. Without vitamin K, clotting factors II, VII, IX and X are unable to be produced. Without these vital parts of the coagulation cascade a durable fibrin plug cannot form to block fluid escaping from damaged or permeable vasculature.
Management
Medication
As well as the routine dose of vitamin K given to newborns after birth, babies born with fetal warfarin syndrome are given additional doses intramuscularly to overcome any remaining warfarin in the circulation and prevent further bleeding. Fresh frozen plasma is also administered to raise concentrations of active blood clotting factors. If the child is anemic from extensive bleeding in-utero, red blood cell concentrate is given to restore oxygen carrying capacity. Surgical correction
Surgical interventions can be given to improve functionality and correct cosmetic abnormalities. Osteotomy (bone cutting) and zetaplasty surgeries are used to cut away abnormal tissue growths at the piriform aperture around and pharynx to reduce airway obstruction. Rhinoplasty surgery is used to restore normal appearance and function of the nose. Heart surgery may also be required to close a patent ductus arteriosus. References
External links

Datagenno - Fetal Warfarin Syndrome