than full anticoagulation but experience is increasing. Indeed,
case reports are starting to emerge where LMWH has been used
for mechanical valve replacements. Compared with UFH the risk
of HIT and osteoporosis are reduced^6 and these heparins may hold
the future for anticoagulation in pregnancy.
Management
Women who do not wish to continue warfarin throughout preg-
nancy can be reassured that conceiving on warfarin appears safe
but conversion to heparin, to avoid the risk of embryopathy,
needs to be carried out by 6 weeks. Breast-feeding on either
warfarin or heparin is safe. Possible regimes include:
- Warfarin throughout pregnancy until near term and then
conversion to unfractionated heparin.
- Unfractionated heparin for the first trimester. Warfarin until
near term and then resumption of heparin.
RReeffeerreenncceess
1 Oakley CM. Anticoagulants in pregnancy.Br Heart J1995; 7744 : 107–11.
2 Cotrufo M, de Luca TSL, Calabro R et al. Coumarin anticoagulation
during pregnancy in patients with mechanical valve prostheses. Eur J
Cardiothorac Surg1991; 55 : 300–5.
3 Maternal and Neonatal Haemostasis Working Party of the Haemostasis
and Thrombosis Task Force. Guidelines on the prevention, investi-
gation and management of thrombosis associated with pregnancy. J
Clin Pathol 1993; 4466 : 489–96.
4 Ginsberg JS, Hirsh J. Use of antithrombotic agents during pregnancy.
Chest1995; 110088 ((ssuuppppll 44 )): 305S–11S.
5 Salazar E, Izaguirre R, Verdejo J et al. Failure of adjusted doses of
subcutaneous heparin to prevent thromboembolic phenomena in
pregnant patients with mechanical cardiac valve prostheses. J Am Coll
Cardiol1996; 2277 : 1698–703.
6 Hirsh J. Low-molecular weight heparin for the treatment of venous
thromboembolism. Am Heart J 1998; 113355 ((ssuuppppll 66 )): S336–42.