Anemia is common in fetuses exposed to warfarin as blood constantly seeps into the interstitial fluid or amniotic cavity. High doses of warfarin and heavy bleeding lead to abortion and stillbirth. Osteocalcin is another protein dependent on vitamin K for correct folding and function. Osteocalcin is normally secreted by osteoblast cells and plays a role in aiding correct bone mineralization and bone maturation. In the presence of warfarin and subsequent absence of vitamin K and active osteocalcin, bone mineralization and growth are stunted. Prevention
Fetal warfarin syndrome is prevented by withholding prescription to pregnant women or those trying to conceive. As warfarin can remain in the mothers body for up to five days, warfarin should not be administered in the days leading up to conception. Doctors must take care to ensure women of reproductive age are aware of the risks to the baby should they get pregnant, before prescribing warfarin. For some women, such as those with prosthetic heart valves, anticoagulation medication cannot be suspended during pregnancy as the risk of thrombus and emboli is too high. In such cases an alternate anticoagulant, which cannot pass through the placental barrier to the fetus, is proscribed in place of warfarin. Heparin is one such anticoagulant medication, although its efficacy in patients with prosthetic heart valves is not well established. New anticoagulant medications, which are efficacious and non-teratogenic such as ximelagatran continue to be developed.
Fetal warfarin syndrome is a disorder of the embryo which occurs in a child whose mother took the medication warfarin (brand name: Coumadin) during pregnancy. Resulting abnormalities include low birth weight, slower growth, intellectual disability, deafness, small head size, and malformed bones, cartilage, and joints.Warfarin is an oral anticoagulant drug (blood thinner) used to reduce blood clots, deep vein thrombosis, and embolism in people with prosthetic heart valves, atrial fibrillation, or those who have had ischemic stroke. Warfarin blocks the action of vitamin K, causing an inhibition of blood clotting factors and the pro-bone-building hormone osteocalcin. Warfarin is a teratogen which can cross from the mother to the developing fetus. The inhibition of clotting factors can lead to internal bleeding of the fetus while the inhibition of osteocalcin causes lower bone growth. As well as birth defects, warfarin can induce spontaneous abortion or stillbirth. Because of this, warfarin is contraindicated during pregnancy. Signs and symptoms
The key symptoms, visible at birth, vary between individuals exposed to warfarin in utero. The severity and occurrence of symptoms is dose dependent with higher doses (>5 mg warfarin daily) more likely to cause immediately noticeable defects.The period of pregnancy in which warfarin is administered can affect the category of defects which develop. Warfarin taken in the first trimester of pregnancy is more likely to result in physical abnormalities while warfarin taken in the second and third trimester more commonly causes abnormalities of the central nervous system.