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20-01-2011 | Cardiology | Article

Efficacy of low-dose LMWH during pregnancy and postpartum questioned


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MedWire News: Dutch researchers have questioned the effectiveness of low-dose low-molecular-weight heparin (LMWH) to prevent venous thromboembolism (VTE) during pregnancy and postpartum.

Their retrospective cohort study suggested that one in 20 women at intermediate or high risk for pregnancy-related VTE experienced these events despite prophylaxis with low-dose LMWH.

All VTE events occurred in women considered to be at high risk for such events, and they were notably common during the postpartum period.

The bleeding complication of postpartum hemorrhage occurred frequently, although at a similar rate in women who started LMWH after giving birth and those who used it during pregnancy.

The researchers say: "In our study, low-dose LMWH prophylaxis was associated with considerable treatment failure both antenatal and postpartum, in particular in women with a high risk of recurrent VTE."

The team, led by Jeanine Roeters van Lennep (Erasmus Medical Center, Rotterdam), studied 34 women at intermediate risk for pregnancy-related VTE, who had 44 pregnancies for which they received low-dose LMWH for 6 weeks postpartum.

The researchers also studied 57 women at high risk for VTE. These women had a total of 82 pregnancies and received low-dose LMWH during pregnancy as well as for 6 weeks afterwards.

Pregnancy-related VTE, defined as VTE during pregnancy or within 3 months postpartum, occurred in 5.5% of participants despite low-dose LMWH prophylaxis.

All events occurred in women at high VTE risk, with a postpartum incidence of 7.0% and an antepartum incidence of 1.8%.

The risk for postpartum hemorrhage, defined as blood loss of less than 500 ml, was 21.6%, while the risk for severe post-partum hemorrhage, in which blood loss was more than 1000 ml, was 9.1%.

Reporting in the Journal of Thrombosis and Haemostasis, the researchers conclude: "Although current guidelines support the use of low-dose LMWH during pregnancy and postpartum as VTE prophylaxis in pregnant women, this dose might not be sufficient.

"A randomized trial comparing low-dose LMWH to high-dose LMWH in pregnant women at high risk of VTE would solve this issue."

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Anita Wilkinson

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