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Thrombosis in pregnancy 

Thrombosis in pregnancy

Thrombosis in pregnancy

I.A. Greer


November 30, 2011: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

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date: 28 April 2017

Aetiology—features that predispose to venous thromboembolism include (1) pregnancy is a thrombophilic state; (2) there is relative venous stasis during pregnancy; and (3) some endothelial damage to the pelvic vessels occurs during delivery.

Epidemiology— venous thromboembolism complicates around 1 in 1000 pregnancies, with highest risk just after delivery. Deep venous thromboses usually occur on the left side, and a much higher proportion are ileofemoral than in patients who are not pregnant.

Screening—there is no evidence to support universal screening for thrombophilia in pregnancy, but such screening is appropriate for women with a personal or well-proven family history of venous thromboembolism, also in patients who might reasonably be suspected of having antiphospholipid antibody syndrome.

Diagnosis—ultrasound venography is the first line diagnostic test for deep venous thrombosis in pregnancy. If pulmonary thromboembolism is suspected, ultrasound venography of the leg veins can also be performed: if positive anticoagulation can be given; if negative a chest radiograph and ventilation–perfusion scan or CT pulmonary angiogram are required.

Management—low molecular weight heparin (LMWH) is the anticoagulant of choice in pregnancy because of a better side-effect profile than warfarin or unfractionated heparin, good safety record for mother and fetus, and convenient once-daily dosing for prophylaxis. Typical recommendations are as follows: (1) prophylaxis for women at low but still probably increased risk, e.g. history of previous venous thromboembolism that was not pregnancy-related, associated with a risk factor that is no longer present, and with no additional risk factor or underlying thrombophilia can be offered surveillance antenatally, with postpartum anticoagulation therapy (usually with LMWH) for at least 6 weeks; antenatal LMWH would not be routinely given. (2) Prophylaxis for women at higher risk of recurrent venous thromboembolism in pregnancy—these should usually be prescribed prophylactic LMWH, which should be started as soon as possible following the diagnosis of pregnancy and continued for at least 6 weeks after delivery. (3) Treatment of proven venous thromboembolism in pregnancy—in most cases a twice-daily regimen (because of increased renal excretion) of LMWH is the treatment of choice, but intravenous unfractionated heparin remains the preferred treatment in massive pulmonary thromboembolism.

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