[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Teratology and prenatal diagnosis](https://durgical.com/en/embryology/#a-teratology) › Warfarin embryopathy [Embryology](https://durgical.com/en/embryology/) · [Teratology and prenatal diagnosis](https://durgical.com/en/embryology/#a-teratology) # Warfarin embryopathy - Teratogen Warfarin, a blood thinner, can disturb the embryo's bones and nose and, later, cause bleeding in the fetal brain. Updated 2026-11-01 **See it in 3D:** [Nasal bones](https://durgical.com/en/anatomy/nasal-bone/) · [Nasal cartilages](https://durgical.com/en/anatomy/major-alar-cartilage/) · [Humerus](https://durgical.com/en/anatomy/humerus/) · [Femur](https://durgical.com/en/anatomy/femur/) ## Key points - Critical period for the embryopathy: gestational weeks 6 to 9. - Nasal hypoplasia (small nose with a depressed bridge) and stippled epiphyses (chondrodysplasia punctata). - Second- and third-trimester exposure: fetal haemorrhage with microcephaly, hydrocephalus, Dandy-Walker malformation and optic atrophy. - Heparin, a large charged molecule, does not cross the placenta and is not teratogenic. - Anticoagulation in pregnancy (for example with mechanical valves) is decided by the treating team. ## What it is Warfarin is a vitamin K antagonist that crosses the placenta. Early in pregnancy it stops vitamin K–dependent bone and cartilage proteins from being activated, giving the classic embryopathy: nasal hypoplasia and stippled epiphyses. Later the risk is fetal bleeding with central nervous system damage. Heparin does not cross the placenta. ## Key facts - Mechanism: blocks gamma-carboxylation of vitamin K–dependent proteins. - These include clotting factors and matrix proteins of bone and cartilage. - Other findings: choanal atresia or stenosis, limb hypoplasia and short stature. - Warfarin is also linked to miscarriage and stillbirth. - It is a small molecule that crosses the placenta easily. ## Critical period and mechanism - Critical period: gestational weeks 6 to 9 for the skeletal defects. - It inhibits vitamin K epoxide reductase, leaving proteins with gamma-carboxyglutamic acid residues inactive. - Without those proteins, cartilage calcifies in abnormal spots (stippled epiphyses) and the nasal skeleton grows little. - In the fetus, the lack of active clotting factors favours bleeding into the brain and other organs. ## Prevention - Preconception counselling for anticoagulated women to plan treatment. - The treating team (cardiology and obstetrics) chooses the right anticoagulant for each stage of pregnancy. - Medicines in pregnancy are decided with the treating professional, never stopped on one's own. ## What it does to the embryo and fetus - Hypoplastic nose with a depressed nasal bridge; breathing difficulty from choanal stenosis. - Stippled calcifications of the epiphyses on X-ray; short limbs. - From haemorrhage: microcephaly, hydrocephalus, Dandy-Walker, optic atrophy and intellectual disability. - Miscarriage or stillbirth. ## Memory aid Warfarin 'steals the K from bone': a flat nose and epiphyses 'dotted' with calcium. ## Test yourself Think of the answer, then tap the question to see it. ## What are the two classic findings of warfarin embryopathy? Nasal hypoplasia and stippled epiphyses (chondrodysplasia punctata). ## In which gestational weeks is the risk of warfarin embryopathy highest? Between gestational weeks 6 and 9. ## Why does heparin not cause this embryopathy? It is a large, charged molecule that does not cross the placenta. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/embryology/warfarin-embryopathy/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Nasal bones](https://durgical.com/en/anatomy/nasal-bone/) - [Nasal cartilages](https://durgical.com/en/anatomy/major-alar-cartilage/) - [Humerus](https://durgical.com/en/anatomy/humerus/) - [Femur](https://durgical.com/en/anatomy/femur/) ## Related - [Congenital hydrocephalus: aqueductal stenosis](https://durgical.com/en/embryology/congenital-hydrocephalus-aqueductal-stenosis/) - [Dandy–Walker malformation](https://durgical.com/en/embryology/dandy-walker-malformation/) - [Skull: neurocranium, viscerocranium, sutures and fontanelles](https://durgical.com/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/) - [Limb development: the apical ectodermal ridge, ZPA and limb rotation](https://durgical.com/en/embryology/limb-development-the-apical-ectodermal-ridge-zpa-and-limb-rotation/) - [Microcephaly](https://durgical.com/en/embryology/microcephaly/) - [Principles of teratology: critical periods, dose and genotype](https://durgical.com/en/embryology/principles-of-teratology-critical-periods-dose-and-genotype/) ## Related conditions - [Atrial fibrillation](https://durgical.com/en/conditions/atrial-fibrillation/) - [Deep vein thrombosis](https://durgical.com/en/conditions/deep-vein-thrombosis/) - [Pulmonary embolism](https://durgical.com/en/conditions/pulmonary-embolism/) - [Rheumatic heart disease](https://durgical.com/en/conditions/rheumatic-heart-disease/) - [Mitral stenosis](https://durgical.com/en/conditions/mitral-stenosis/) ## In Pharmacology - [Warfarin](https://durgical.com/en/pharmacology/warfarin/) - [Heparin](https://durgical.com/en/pharmacology/heparin/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Teratogenic Medications](https://www.ncbi.nlm.nih.gov/books/NBK553086/) (StatPearls Publishing (NCBI Bookshelf), 2024); Langman's Medical Embryology, 13th ed., ch. 9: Birth Defects and Prenatal Diagnosis (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/warfarin-embryopathy/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/warfarin-embryopathy/