Abnormalities of the chest: either pectus carinatum; a protruding sternum, or pectus excavatum; a sunken sternum form an immediately recognizable sign of fetal warfarin syndrome. Congenital heart defects such as a thinned atrial septum, coarctation of the aorta, patent ductus arteriosus; a connection between the pulmonary artery and aorta occur in 8% of fetal warfarin syndrome patients. Situs inversus totalis, the complete left-right mirroring of thoracic organs, has also been observed

CNS
Defects of the central nervous system can lead to profound intellectual disabilities. Fetal warfarin syndrome can lead to microcephaly; an abnormally small head, hydrocephaly; increased ventricle size and CSF volume, and agenesis of the corpus callosum. These defects contribute to the appearance of significant intellectual disability in 31% of fetal warfarin syndrome cases. Hypotonia, whole body muscle relaxation, can appear in newborns with severe nervous deficits. Atrophy of the optic nerve can also cause blindness in fetal warfarin syndrome. Physiological
Inhibition of coagulation and resultant internal bleeding can cause too few red blood cells to be present in the bloodstream and low blood pressure in newborns with fetal warfarin syndrome. Low hemoglobin levels can lead to partial oxygen starvation, a high level of lactic acid in the bloodstream, and acidosis. Prolonged oozing of fluid from the stump of the cut umbilical cord is common. Cause
Fetal warfarin syndrome appears in greater than 6% of children whose mothers took warfarin during pregnancy. Warfarin has a low molecular weight so can pass from the maternal to fetal bloodstream through the tight filter-like junctions of the placental barrier.
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.