Oral anticoagulation therapy during pregnancy in patients with mechanical mitral valves: a prospective study

Reports on phenindione toxicity have limited its use as an oral anticoagulant. Our aim was to evaluate its risks in pregnant women. Thirty-one pregnancies in 29 women with mitral (+/-aortic) St. Jude mechanical valves were followed-up prospectively. Eighteen patients received phenindione. Eleven patients (37.9%) received in addition to phenindione 225 mg dipyridamole, which was given in three doses. The target INR was 2.5-3.5 in the former and 2-2.5 in the latter treatment. A fortnight before delivery, intravenous heparinotherapy was substituted. There were no maternal complications, apart from a single postpartum hemorrhage (3.2%). After the deliveries the results were: 26 mature babies (83.9%), 3 premature babies (9.7%) and 2 cases of stillbirth (6.4%). Outcome was dose related; being 57.2+/-20.9 mg/day for mature babies and 82.5+/-11.2 mg/day for prematures and stillbirths (P=0.016). Phenindione provided safe and effective anticoagulation during pregnancy. A larger study is necessary to confirm the relationship between the dosage and outcome.