A woman who took warfarin throughout the first trimester delivers an infant with nasal hypoplasia, stippled epiphyses and limb shortening. The critical window for this teratogenic effect is:
- A Weeks 2 to 4 post-conception
- B Weeks 20 to 24 post-conception
- C Weeks 6 to 12 post-conception ✓
- D The third trimester only
Correct answer: C. Weeks 6 to 12 post-conception
Explanation
Warfarin embryopathy (nasal hypoplasia, stippled epiphyses, limb hypoplasia) results from impaired bone morphogenesis during weeks 6 to 12 of gestation, so warfarin is avoided in the first trimester. Third trimester exposure instead risks fetal intracranial haemorrhage due to fetal factor deficiency at delivery. Heparins do not cross the placenta and are the standard substitutes in pregnancy.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.