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12-05-2011 | Cardiology | Article

Activated protein C resistance increases pregnancy-related thrombosis risk


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MedWire News: Activated protein C (aPC) resistance is associated with a history of pregnancy-related venous thrombosis, regardless of whether the women are carriers or noncarriers of the rs6025 polymorphism in the factor V gene (F5), researchers report.

The F5 rs6025 polymorphism (also known as factor V leiden) is the most common cause of aPC resistance, a condition that is known to increase the risk for venous thrombosis in the general population, explain Per Morten Sandset (University of Oslo, Norway) and colleagues.

Acquired aPC resistance in the absence of F5 rs6025 has been observed in pregnant women, but there is limited information on whether aPC resistance in the absence of F5 rs6025 is associated with venous thrombosis during pregnancy or postpartum, they add.

To address this, Sandset and team studied 313 women with a history of pregnancy-related deep vein thrombosis, pulmonary embolism, or venous thrombosis at unusual sites. A further 353 women with no such history acted as a control group.

The researchers used calibrated automated thrombography to determine sensitivity to aPC and the normalized aPC sensitivity ratio (n-aPC-sr) among the women, who were all between 3 and 16 years past the index pregnancy.

As reported in the British Journal of Haematology, the median n-aPC-sr was significantly higher among the cases, compared with the controls, at 0.53 versus 0.40.

Among women who did not carry F5 rs6025, the risk for pregnancy-related venous thrombosis was a significant 2.4-fold higher for those in the highest quartile (>2.90) of n-aPC-sr compared with those in the lower quartiles.

Adjustment for free protein S and free tissue factor pathway inhibitor, which were inversely associated with n-aPC-sr in women without the polymorphism, did not alter the association.

In addition, women who did carry the F5 rs6025 polymorphism had an increasing risk for venous thrombosis with increasing n-aPC-sr, but the differences between the quartiles were not statistically significant.

"Our findings substantiate the importance of the aPC resistant phenotype as a risk factor for pregnancy-related venous thrombosis," conclude Sandset and co-authors.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Laura Dean

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