Venous thromboembolism (VTE) remains one of the main direct causes of maternal death in the UK and sequential reports on Confidential Enquiries into Maternal Deaths have highlighted failures in obtaining objective diagnoses and employing adequate treatment (1):
- recent years, there has been a significant decline in maternal deaths from VTE in the UK (18 deaths between 2006 and 2008 compared to 41 in 2003–2005), in part owing to better recognition of women at risk and more widespread use of thromboprophylaxis
- prevalence of ultimately diagnosed PE in pregnant women with suspected PE is 2–6%
- risk of antenatal VTE is four- to five-fold higher in pregnant women than in nonpregnant women of the same age, although the absolute risk remains low at around 1 in 1000 pregnancies
- venous thromboembolism can occur at any stage of pregnancy but the puerperium is the time of highest risk, with estimates of relative risk of approximately 20-fold
Risk factors for VTE in pregnancy or in women who have given birth within the previous 6 weeks (2):
- consider offering pharmacological VTE prophylaxis with LMWH (or UFH for patients with renal failure) to women who are pregnant or have given birth within the previous 6 weeks who are admitted to hospital but are not undergoing surgery, and who have one or more of the following risk factors:
- expected to have significantly reduced mobility for 3 or more days
- active cancer or cancer treatment
- age over 35 years
- critical care admission
- dehydration
- excess blood loss or blood transfusion
- known thrombophilias
- obesity (pre-pregnancy or early pregnancy BMI over 30 kg/m2)
- one or more significant medical comorbidities (for example: heart disease; metabolic, endocrine or respiratory pathologies; acute infectious diseases; inflammatory conditions)
- personal history or a first-degree relative with a history of VTE
- pregnancy-related risk factor (such as ovarian hyperstimulation, hyperemesis gravidarum, multiple pregnancy or pre-eclampsia)
- varicose veins with phlebitis.
- consider offering combined VTE prophylaxis with mechanical methods and LMWH (or UFH for patients with renal failure) to women who are pregnant or have given birth within the previous 6 weeks who are undergoing surgery, including caesarean section
- mechanical and/or pharmacological VTE prophylaxis should be offered to women who are pregnant or have given birth within the previous 6 weeks only after assessing the risks and benefits and discussing these with the woman and with healthcare professionals who have knowledge of the proposed method of VTE prophylaxis during pregnancy and post partum. Plan when to start and stop pharmacological VTE prophylaxis to minimise the risk of bleeding
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Clinical features (1):
- majority of women with VTE in pregnancy have clinical symptoms
- symptoms and signs of DVT include leg pain and swelling (usually unilateral) and lower abdominal pain (reflecting extension of thrombus into the pelvic vessels and/or development of a collateral circulation) and the symptoms of PE include dyspnoea, chest pain, haemoptysis and collapse
- is noteworthy that a low-grade pyrexia and leucocytosis can occur with VTE
Diagnosis in pregnancy (1):
- any woman with symptoms and/or signs suggestive of VTE should have objective testing performed expeditiously and treatment with low-molecular-weight heparin (LMWH) given until the diagnosis is excluded by objective testing, unless treatment is strongly contraindicated
- diagnosis of an acute DVT:
- compression duplex ultrasound should be undertaken where there is clinical suspicion of DVT
- if ultrasound is negative and there is a low level of clinical suspicion, anticoagulant treatment can be discontinued
- if ultrasound is negative and a high level of clinical suspicion exists, anticoagulant treatment should be discontinued but the ultrasound should be repeated on days 3 and 7
- diagnosis of an acute pulmonary embolism (PE)
- women presenting with symptoms and signs of an acute PE should have an electrocardiogram (ECG) and a chest X-ray (CXR) performed
- In women with suspected PE who also have symptoms and signs of DVT, compression duplex ultrasound should be performed
- if compression ultrasonography confirms the presence of DVT, no further investigation is necessary and treatment for VTE should continue
- in women with suspected PE without symptoms and signs of DVT, a ventilation/perfusion (V/Q) lung scan or a computerised tomography pulmonary angiogram (CTPA) should be performed
- if the chest X-ray is abnormal and there is a clinical suspicion of PE, CTPA should be performed in preference to a V/Q scan
- alternative or repeat testing should be carried out where V/Q scan or CTPA is normal but the clinical suspicion of PE remains. Anticoagulant treatment should be continued until PE is definitively excluded
- women with suspected PE should be advised that, compared with CTPA, V/Q scanning may carry a slightly increased risk of childhood cancer but is associated with a lower risk of maternal breast cancer; in both situations, the absolute risk is very small
Treatment of pregnancy associated pulmonary embolism (3):
- DOACs and fondaparinux cross the placenta and should be avoided in pregnancy
- unfractionated heparin and LMWH are safest during pregnancy as they do not cross the placenta; LMWH is the mainstay of treatment owing to its once daily dosing and self-administered subcutaneous route
- management of anticoagulation around the time of delivery requires close coordination with a multidisciplinary team of obstetrics, anesthesia, thrombosis, and maternal fetal medicine.
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