The Teratogenic Effects of Warfarin on Fetuses

Abstract

Warfarin causes several teratogenic effects when administered during pregnancy. The resulting fetal disorder is known as fetal warfarin syndrome, or warfarin embryopathy. The resulting adverse effects mainly include phenotypic abnormalities of a hypoplastic nose, stippled epiphyses, abnormalities of the skeleton, as well as several ocular abnormalities. Anticoagulation therapy is deleterious to normal fetal development, whether using warfarin or heparin. However, heparin administration is more strongly advised due to a larger number of studies showing higher safety for normal fetal development. As a result, if a woman who has blood-clotting problems wants to become pregnant, the general consensus among physicians is heparin administration. This, however, still has high risks of fetal adverse effects. The reason for this review was to show how and when warfarin affects a developing fetus and to strongly advise pregnancy screens for pre-menopause female patients who are being administered warfarin. When a patient is taking warfarin, he or she must have weekly, fortnightly, or monthly blood tests for his or her prothrombin time. This PT/INR (prothrombin and internationalized ratio) test is important as a result of the small margin between embolism prevention and hemorrhage prevention. Therefore, physicians must order a standing order for prothrombin times, and the patient must have routine blood work as a result. It is vital that these standing orders for premenopause women not only call for prothrombin tests, but also serum pregnancy tests. With routine pregnancy screening, warfarin administration is less likely to cause teratogenic effects since it will be discontinued early on in the pregnancy. Having routine pregnancy tests is especially important since warfarin is most harmful to the developing fetus in the first trimester, when little visible changes are occurring that might help acknowledge a pregnancy.