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Pregnant woman with hand resting on stomach.

You are 4-5x more likely to have a blood clot if pregnant

Blood clot prevention

Contributor

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Jackie Haigney

Essential Insights contributor, healthcare writer

Featured expert

William Nadeau Medical Affairs Manager, Cardinal Health

William Nadeau, MS, RD

Medical Affairs Director, Cardinal Health

I t’s true. Pregnant women are at greater risk than non-pregnant women for venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE). And the annual incidence of VTE is five times higher in the weeks following birth in pregnant women compared with non-pregnant women, with the incidence of DVT three times higher.

Why?

Physiologic and anatomic changes of pregnancy make both pregnant women and women who just gave birth more susceptible to VTE.

In clinical terms, the increased production of fibrin, decreased fibrinolytic activity and slowed blood flow from the enlarged uterus pressing on the inferior vena cava and pelvic veins lead to a hypercoaguable state in pregnancy. These changes put pregnant women at higher risk of blood clots.

At the same time, pregnancy brings a 20% to 25% increase in overall circulatory volume. The right iliac artery compresses the left iliac vein, which may explain the high incidence of DVT in the left leg during pregnancy.

These effects may be exacerbated when a pregnant woman lies on her back for prolonged periods, such as during bed rest, and blood flow velocity decreases. By 25 to 29 weeks of gestation, venous blood flow velocity in the legs decreases by almost half, a change that lasts until approximately six weeks after delivery.

How to reduce the incidence of VTE? Prevention is key.

The first step is to be aware of the risk for this potentially fatal condition. Pregnant patients should be assessed for risk before they deliver, as they move from an outpatient to inpatient setting, and after birth.

If a patient’s condition and/or history indicate the need for thromboprophylaxis, it’s important to choose an appropriate strategy. Preventive measures typically involve anticoagulation agents or the use of mechanical devices, including Graduated Compression Stockings (GCS) or intermittent pneumatic compression (IPC) devices to address risk.

Anticoagulants or mechanical compression?

Although anticoagulants are used to reduce risk of VTE, they can introduce other issues. The Royal College of Obstetriacians & Gynecologists (RCOG ) guidelines note that after C-section there is an increased risk of wound hematoma of about two percent with both unfractionated heparin (UH) and low-molecular-weight heparin (LMWH).

Birth planning timeline - VTE Prophylaxis

This timeline superimposes the recommended uses of both therapies to show how IPC devices can be used to reduce the risk of VTE ― both before and after delivery.
Chart - VTE Prophylaxis.

The use of anticoagulants in C-Sections

Scenario 1

  • To avoid the risk of epidural hematoma, RCOG recommends that regional anesthesia and analgesia not be used until at least 12 hours after the last dose of LMWH has been administered.

Scenario 2

  • If a woman has been on a therapeutic regimen of LMWH antenatally, regional techniques should not be used for at least 24 hours after the last dose of LMWH.
  • In either scenario, a new dose of LMWH should not be administered until at least four hours post-delivery, according to RCOG.

No Anticoagulants

  • Compression therapy provides an effective method of VTE prophylaxis without the potential problems posed by anticoagulants. Both the RCOG and American College of Obstetricians and Gynecologists (ACOG) recommend the use of compression therapy to help prevent VTE.

GCS

  • RCOG recommends that pregnant women with three or more persisting VTE risk factors should be given Graduated Compression Stockings (GCS).

IPC Devices

  • ACOG recommends the use of IPC devices prior to C-section delivery for pregnant women who are not receiving thromboprophylaxis. ACOG also recommends the continued use of IPC devices until the patient is ambulatory and anticoagulation therapy is restarted, when anticoagulation therapy is determined necessary after delivery.
  • In 2011, ACOG published an opinion supporting the routine use of perioperative IPC devices during C-section. IPC devices reduce the risk of VTE by increasing femoral blood flow through mechanical compression of the lower limbs, as well as by stimulating fibrinolysis through an increase in tissue plasminogen activator concentration and a decrease in inhibitor levels. However, in order to effectively prevent VTE, IPC devices should be used continuously, since their beneficial effects are lost within 10 minutes of their removal.