Anticoagulation in pregnant heart valve patients. (Warfarin Calleed Reasonable Approach).

SNOWMASS, COLO. -- Continued use of warfarin throughout pregnancy is a reasonable management strategy in selected women with a prosthetic heart valve, Dr. Carole A. Warnes said at a conference sponsored by the American College of Cardiology.

Appropriate candidates are women on lower-dose warfarin before pregnancy and at high risk for a thromboembolic event during pregnancy, either because of a history of prior events or because they have an older tilting-disk mechanical valve in the mitral position, said Dr. Warnes, professor of medicine at the Mayo Clinic, Rochester, Minn.

Unfractionated heparin is a less attractive option in these high-risk patients. It's a much less effective antithrombotic agent than warfarin during pregnancy she added.

The chief downside of warfarin use in pregnancy is the risk of embryopathy with fetal exposure during weeks 6-9. But there is evidence to suggest this risk is probably dose-related. One showed no embryopathy in 33 exposed fetuses whose mothers were on 5 mg/day or less of warfarin, compared with a 9% incidence of warfarin embryopathy in 25 fetuses whose mothers were on higher doses. However, this study was a retrospective case series, and there have been no controlled trials to guide management of thromboembolic risk in pregnant patients with prosthetic valves.

While warfarin dosage requirements can change frequently during pregnancy a woman who is well controlled on 5 mg/day or less prior to pregnancy usually won't need more than 5 mg/day during pregnancy she said.

Warfarin embryopathy is marked by mental retardation, optic atrophy nasal hypoplasia, and cataracts. But the risk of warfarin embryopathy following fetal exposure is often overstated in the literature. Rates quoted in various series range ...