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Warfarin versus low molecular weight heparin: a comparison of adverse outcomes in pregnant women with mechanical heart valves
  1. C Hein,
  2. S Basude,
  3. S Curtis,
  4. K Collins,
  5. J Trinder
  1. University Hospitals Bristol, Bristol, UK


A consensus is yet to be reached regarding the anticoagulation regimen that is both safe for the fetus and effective for women with mechanical heart valves in pregnancy.

We compared the outcomes and adverse events in women with mechanical heart valves attending the tertiary cardiac antenatal clinic (University Hospitals Bristol, 2003–2010). Women were offered anticoagulation with low molecular weight heparin/aspirin(LMWHa), Warfarin or a Combination regimen(LMWHa from 6 weeks/warfarin 14–36 weeks/LMWHa 36+). All women were informed that warfarin was likely to be the safest option for them, although not for the fetus.

Results A total of 30 pregnancies in 15 women were identified. Aortic (13), aortic/mitral (2), mitral (12), tricuspid (3). Women were anticoagulated with LMWHa (3), Warfarin (21) and Combination (6). Rates of pregnancy loss before 24 weeks were 0/3 LMWHa, 16/21 Warfarin (dose range 4–13 mg), 3/6 Combination (two 2nd trimester after restarting warfarin). Live births were achieved in 2/3 women (LMWHa), 5/21 (Warfarin) and 3/6 (Combination).

There were eight adverse maternal events: TIA (Combination) at 9 weeks while on LMWHa (the patient was non-compliant), maternal death from a parietal haemorrhage at 8 weeks (LMWHa) and a mitral valve thrombosis at 35 weeks (LMWHa), both patients were compliant with peak Anti-Xa 1.0–1.2 IU/ml. Postpartum or postspontaneous abortion haemorrhage occurred in five women (3/21 Warfarin, 1/3 LMWHa, 1/6 Combination).

Conclusions Warfarin is associated with an unacceptably high fetal loss rate, but severe adverse maternal outcomes are associated with LMWHa, even when therapeutic peak anti-Xa levels are achieved. A national database to collect this information is recommended.

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