Fetal warfarin syndrome can be seen in babies whose mothers took warfarin, an anticoagulant or blood thinner, during pregnancy. An anticoagulant stops blood clots from forming and moving throughout the body. Warfarin can be dangerous to the developing fetus, especially during the first trimester when warfarin can cause early death of the baby or preterm birth. Additionally, warfarin can cause birth defects such as abnormal development of the spine, changes to bones in the face (especially the nose), intellectual disability, and failure to thrive. The risks for taking warfarin later in pregnancy are much lower, but pregnant women should speak to their doctor before taking warfarin at any time during pregnancy in order to best protect their child.