We searched Medline (1996–2008), PubMed (1996–2008), and the Global Health (2002–08), Popline (2002–08), and Cochrane (2002–08) databases with the MeSH headings “pulmonary embolism”, “venous thromboembolism”, “subsegmental emboli”, “pregnancy”, “mortality”, “epidemiology”, “risk factors”, “diagnosis”, “arterial blood gases”, “electrocardiogram”, “ventilation perfusion scan”, “computed tomography pulmonary angiogram”, “magnetic resonance”, “compression ultrasonography”, “echocardiogram”,
SeminarPulmonary embolism in pregnancy
Introduction
Peripartum haemorrhage is the leading cause of maternal mortality in the developing world, reflecting the haemostatic challenge of childbirth.1 The maternal hypercoagulable state is a physiological preparation for delivery; however, this hypercoagulability is associated with an increased risk of venous thromboembolism (VTE). Indeed, in the developed world, where the haemostatic challenge of delivery is mitigated by modern obstetrical practices, VTE is the leading cause of maternal mortality.2, 3, 4, 5, 6
Prevention, diagnosis, and therapeutic management of pulmonary embolism (PE) in pregnant women are all complicated by a shortage of validated approaches in this unique population. In this Seminar, we provide practical recommendations to overcome these challenges.
Section snippets
Epidemiology
The incidence of VTE in pregnant women, derived from retrospective cohort studies, is estimated to be 5–12 events per 10 000 pregnancies antenatally (from conception to delivery), seven to ten times higher than the incidence in age-matched controls. The risk of VTE events is similar in all three trimesters.7 The incidence of pregnancy-associated deep vein thrombosis (DVT) is about three times higher than that of pregnancy-associated PE.8 Pregnancy-associated DVT is left sided in over 85% of
Pathophysiology
The elements of Virchow's triad—venous stasis, vascular damage, and hypercoagulability—are all present during pregnancy and the postpartum period (figure 1). Venous stasis, which begins in the first trimester and reaches a peak at 36 weeks of gestation, is probably caused by progesterone-induced venodilation, pelvic venous compression by the gravid uterus, and pulsatile compression of the left iliac vein by the right iliac artery.19 Additional damage to the pelvic vessels results from normal
Diagnosis
Approaches to diagnostic management of suspected PE in pregnancy have not been validated. The following suggestions are based on a combination of limited data for diagnosis of suspected PE in pregnancy and more abundant data for non-pregnant patients.
A major challenge in the diagnostic management of suspected PE is to reduce the number of false-negative and false-positive results. False-negative results are a concern because untreated VTE, at least outside of pregnancy, has a mortality rate as
Treatment of confirmed PE in pregnancy
LMWH is the treatment of choice for PE in pregnant and non-pregnant patients. LMWH is at least as effective and as safe as UFH in non-pregnant women for the treatment of acute VTE.78, 79 Furthermore, long-term use of LMWH seems as safe and effective as vitamin K antagonists for the prevention of recurrent VTE in non-pregnant patients.78, 79, 80, 81, 82
Treatment of PE can be considered in four phases: acute (first 24 h from diagnosis), subacute (day 1–30), medium term (1–6 months) and long term
Management of isolated subsegmental PE
The shortage of data on clinical outcomes in pregnant or non-pregnant patients with isolated subsegmental PE in whom anticoagulation has been withheld makes management of these emboli difficult. Outcome data for patients who had ventilation perfusion scans interpreted as normal indirectly supports withholding anticoagulation in patients with normal perfusion in the same distribution as a subsegmental PE detected on CT. However, diagnostic and therapeutic management of isolated subsegmental PE
Prevention
Risk assessment should be done to establish the need for thromboprophylaxis during pregnancy and the postpartum period. However, large-scale studies on VTE prophylaxis are scarce; therefore, recommendations are based on studies done in non-pregnant patients, case series of pregnant patients, and consensus recommendations.123, 125 Early mobilisation and graduated compression stockings are mildly effective, safe, and non-invasive methods for prevention of VTE;126 they are probably all that is
Conclusions
The diagnosis and management of PE in pregnancy is complicated by the physiological changes of pregnancy and the paucity of studies done in pregnant patients. Specific areas of future research should concentrate on the following key areas: determination of clinical criteria that would help to predict the likelihood of VTE; assessment of current and new biomarkers of the prothrombotic state, such as D-dimer concentration, and their incorporation into algorithms of thrombotic risk assessment in
Search strategy and selection criteria
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