Haematologica, Vol 94, Issue 11, 1608-1612 doi:10.3324/haematol.2008.002840
Copyright © 2009 by Ferrata Storti Foundation
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Thrombosis

Use of high intensity adjusted dose low molecular weight heparin in women with mechanical heart valves during pregnancy: a single-center experience

John Quinn1, Kate Von Klemperer2, Ruth Brooks2, Donald Peebles3, Fiona Walker2, Hannah Cohen1

1 Departments of Haematology
2 Cardiology
3 Obstetrics and Gynaecology, University College London and University College London Hospitals NHS Foundation Trust, London, UK

Correspondence: Hannah Cohen, Department of Hematology, University College London Hospitals, NHS Foundation Trust, 1st Floor Central, 250 Euston Road, London NW1 2PJ, UK. E-mail:hannah.cohen{at}uclh.nhs.uk

The use of standard dose low molecular weight heparin (LMWH) to anticoagulate women with mechanical valves in pregnancy is associated with morbidity and mortality. We conducted a prospective audit of the use of adjusted dose high intensity LMWH in 12 pregnancies in 11 women with prosthetic heart valves. LMWH ± low-dose aspirin was started at therapeutic-dose with monitoring of anti-Xa levels to achieve a target level of 1.0–1.2 IU/mL (0.8–1.2 in the first 3/12 pregnancies). This necessitated a mean increase in the dose of LMWH of 54.4% (SD±33.2) over initial dose. Eleven of 12 pregnancies resulted in live births, with one intrauterine fetal death at 37 weeks. One non-fatal valve thrombosis occurred at 26 weeks gestation associated with subtherapeutic anti-Xa levels. Three patients experienced major bleeding. This regime provides a therapeutic option for women with mechanical heart valves during pregnancy, provided anti-Xa levels are kept within the target range. These patients require close surveillance for bleeding and thrombotic complications within a multi-disciplinary setting.

Key words: pregnancy, low molecular weight heparin, mechanical heart valves.