Date Published: November 22, 2011
Publisher: Hindawi Publishing Corporation
Author(s): Pelle G. Lindqvist, Margareta Hellgren.
Obstetric thromboprophylaxis is difficult. Since 10 years Swedish obstetricians have used a combined risk estimation model and recommendations concerning to whom, at what dose, when, and for how long thromboprophylaxis is to be administrated based on a weighted risk score. In this paper we describe the background and validation of the Swedish guidelines for obstetric thromboprophylaxis in women with moderate-high risk of VTE, that is, at similar or higher risk as the antepartum risk among women with history of thrombosis. The risk score is based on major risk factors (i.e., 5-fold increased risk of thromboembolism). We present data on the efficacy of the model, the cost-effectiveness, and the lifestyle advice that is given. We believe that the Swedish guidelines for obstetric thromboprophylaxis aid clinicians in providing women at increased risk of VTE with effective and appropriate thromboprophylaxis, thus avoiding both over- and under-treatment.
The incidence of obstetric venous thromboembolism (VTE) in the Nordic countries is estimated at 10 to 13 cases per 10000 pregnancies, half of them diagnosed during the first six weeks after birth [1, 2]. VTE is one of the most common causes of maternal death [3, 4] and leads to morbidity in the form of postthrombotic syndrome in up to 50–60% [5, 6]. Several factors are known to increase the risk of obstetric VTE, such as personal or family history of VTE, thrombophilia, older age, high body mass index (BMI), immobilization, surgery, smoking, nulliparity, and cancer [1, 2].
The available literature from 1996 to 2000 on risk factors for obstetric VTE was reviewed. Two different risk models were constructed, one a weighted risk score based on major risk factors associated with a five-fold increased risk or a multiple thereof [11, 12], and the other an individualized computerized risk assessment using and including estimates of the absolute risk . Hem-ARG, the Swedish Association of Obstetricians and Gynecologists (SFOG) reference and working group on hemostatic disturbances in obstetrics and gynecology, chosed the weighted risk score model. Swedish guidelines based on this model were published in 2004 , and established as a National Guideline by SFOG in 2009. The guidelines were revised in 2010-2011, resulting in the version presented here.
As is evident from Table 2, LMWH thromboprophylaxis is recommended at a risk level corresponding to the antenatal risk of women with one prior VTE. This risk level can also be attained by the simultaneous existence of several risk factors in a woman with no history of VTE. The differences in ante- and postpartum risk (postpartum risk is about five-fold higher) and the quickly decreasing risk after the first postpartum week are taken into account in the scoring system. In the following, we will present “normal-dose” thromboprophylaxis, as recommended for women at moderate-high risk of VTE during pregnancy.
Following the guidelines has been shown to be cost-effective, especially when it comes to postpartum thromboprophylaxis for those with two and three risk points, for whom the cost of thromboprophylaxis is between 25% and 50% of the cost of thrombotic complications . It is important to remember that the cost-effectiveness data is only valid if the guidelines are followed strictly.