Anticoagulation in pregnancy and the puerperium.

For the management of acute thrombotic events in pregnancy therapeutic doses of low molecular weight heparins (LMWH) may be used, unless the shorter half-life of intravenous unfractionated heparin (UH) and predictable reversibility by protamine are important. Treatment should be continued up until delivery and into the puerperium. Pregnant women who have had an acute thrombotic event should be delivered by a specialist team. In the case of recent thrombosis, delivery should be planned and the time during which anticoagulation therapy is ceased around the time of delivery should be minimised. Therapeutic doses of LMWH contraindicate the use of regional anaesthesia, and a switch to intravenous UH before delivery may allow greater flexibility in this regard. Prophylactic doses of LMWH can be used to reduce the risk of recurrent thromboembolic events in pregnancy. The regimen used will depend on the previous history, the family history and the presence of risk factors, including the genetic and acquired causes of thrombophilia. Women with mechanical heart valves are at high risk during pregnancy and require therapeutic anticoagulation throughout pregnancy under the direction of experienced specialists. Low-dose aspirin can reduce the risk of recurrent pre-eclampsia by about 15%, but the role of UH and LMWH in the prevention of recurrent miscarriage or obstetric complications associated with uteroplacental insufficiency is still uncertain.