Venous thromboembolism in pregnancy: Clinical sciences

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Introduction0:00–0:26

Venous thromboembolism, or VTE for short, is when clots form within the venous system, leading to complications that include deep vein thrombosis, or DVT, and pulmonary embolism, or PE.
While patients are at increased risk for VTE as early as the first trimester, their highest risk occurs in the first 1 to 2 weeks postpartum.

Unstable Patient0:26–1:05

If your patient presents with a chief concern suggesting venous thromboembolism in pregnancy, you should first perform an ABCDE assessment to determine if they are stable or unstable.
If unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access and place your patient on continuous vital sign monitoring, including blood pressure, heart rate, and oxygen saturation.
Don’t forget that you have two patients, so be sure to assess fetal heart rate, and depending on gestational age, consider continuous fetal monitoring as well.
Finally, if needed, provide supplemental oxygen. Okay, let’s go back to the ABCDE assessment and talk about stable patients.

Stable patient/DVT1:05–5:33

In this case, start by obtaining a focused history and physical examination. During pregnancy, most cases of VTE are caused by DVT, and unlike non-pregnant patients, the thrombus tends to be more proximal, typically in the iliac vein and iliofemoral veins, and occurs more frequently in the left lower extremity compared to the right.
These patients will usually present with unilateral extremity pain and swelling. History might also reveal some risk factors for DVT, with the most important one being a personal history of thrombosis.
Others include having a C-section; obesity; hypertension, preeclampsia, or eclampsia; and having an acquired or inherited thrombophilia.
The most reliable physical exam finding is a difference in calf circumference measurements of at least 2 centimeters. You might also be able to palpate the thrombotic vein, which could be erythematous, warm, and tender.
Labs are typically not necessary for diagnosis. Time for a clinical pearl!
While serum D-dimer assays are useful to rule out DVT in non-pregnant patients, this test is not reliable during pregnancy and postpartum, as physiologic levels are normally elevated.
Now, if your patient has these history and exam findings, obtain a lower extremity compression ultrasound. If it shows poor compressibility of a proximal lower extremity vein, your diagnosis is DVT.
Treatment begins with therapeutic anticoagulation with low molecular weight heparin, such as enoxaparin. If your patient never had thrombophilia testing, consider the best time interval for it.
While some molecular genetic tests can be performed at any time, other non-molecular tests, such as for Protein C and Protein S deficiencies, should be done at least 3 months postpartum.
Ideally, the best timing for thrombophilia testing is when your patient is not pregnant or lactating, is not taking anticoagulation, and is not taking hormonal contraception.
If maternal and fetal status are reassuring, plan for vaginal delivery at 39 weeks unless otherwise contraindicated. Once your patient has delivered, resume anticoagulation if it was on hold.
Typically you’ll want to continue anticoagulation for at least 3 months, which includes the 6 week postpartum window. The actual duration of anticoagulation varies depending on your patient’s history.
For those who require anticoagulation for more than 6 weeks postpartum, consider transitioning to oral therapy with warfarin.
Here are a couple of high-yield facts! Warfarin, a vitamin K antagonist, is often used for long-term anticoagulation outside of pregnancy.
It’s rarely used during pregnancy, except in those with a high thrombotic risk, such as having a mechanical heart valve.
That’s because it can cause warfarin embryopathy in the first trimester and may cause significant fetal hemorrhage later in pregnancy if delivery occurs unexpectedly.
So, if your patient requires warfarin, it should be replaced with unfractionated heparin in the first trimester and around the time of delivery.
On the flip side, warfarin is compatible with breastfeeding, since it doesn’t accumulate in breast milk and doesn’t cause an anticoagulation effect on the newborn.
Therefore, lactating patients who require long-term anticoagulation can be transitioned to warfarin postpartum. Additionally, oral direct thrombin inhibitors, such as dabigatran; and Factor-Xa inhibitors, such as rivaroxaban, should be avoided in pregnancy and lactation because there are insufficient data to ensure maternal or fetal safety, and their effects are unknown on the breastfeeding neonate.
Here’s another clinical pearl! The shorter half-life of unfractionated heparin makes it a good choice for transitioning in preparation for labor and delivery, to allow your patient the option of receiving neuraxial anesthesia.
Depending on the type and dose of medication used, anticoagulation should be held for 12 to 24 hours before the patient receives neuraxial anesthesia.

PE5:33–9:44

Alright, now that we’ve discussed DVT in pregnancy, let’s discuss a less common but more severe form of VTE called pulmonary embolism.
These patients typically present with sudden-onset dyspnea, and may have pleuritic chest pain, palpitations, and hemoptysis.
Similar to DVT, they might experience unilateral extremity pain and swelling, and have risk factors such as a personal history of thrombosis; c-section; obesity; preeclampsia or eclampsia; or an acquired or inherited thrombophilia.
On physical exam, they may have abnormal vital signs, such as tachycardia, tachypnea, hypoxia, or hypotension. Chest auscultation might reveal rales or even absent breath sounds.
Again, you might find signs of DVT, including a differential calf circumference of 2 centimeters or more; as well as a palpable thrombotic vein with focal lower extremity erythema, tenderness, and warmth.
If you see these findings, obtain a lower extremity compression ultrasound. Now, if there is poor compressibility of a proximal vein on ultrasound, you can skip chest imaging and treat them as having a DVT with a presumptive pulmonary embolism.
Let’s talk about different ultrasound findings. If there is no evidence of venous thrombosis on ultrasound, you should get a chest x-ray to look for signs of pulmonary disease.
So, if the chest x-ray returns normal, perform a ventilation-perfusion scan, also known as V/Q scan. If it’s normal too, consider an alternative diagnosis.
However, if the V/Q scan demonstrates a high probability for thrombus, then your diagnosis is pulmonary embolism. Here’s a clinical pearl!
If the V/Q scan returns with a low or medium priority result or is technically inadequate, proceed with a CT pulmonary angiogram or CTPA for definitive diagnosis.
While there is no evidence to determine the superiority of either V/Q scan or CTPA, many institutions are utilizing CTPA as the initial test of choice to evaluate for pulmonary embolism in pregnancy.
Okay, back to the chest X-ray. If you see evidence of pulmonary disease, CTPA is the next step.
If it’s normal, consider an alternative diagnosis. However, if CTPA demonstrates a clot, then your diagnosis is pulmonary embolism.
Time for another clinical pearl! Both V/Q scan and CTPA, are associated with relatively low fetal radiation exposure, and both are reasonable choices for ruling out PE in pregnancy.
The decision on which test to perform is based not only on the results of the chest X-ray, but is also dependent on institutional protocols, local availability and expertise, and other considerations, such as whether your patient has a contrast allergy.
Managing pulmonary embolism in pregnancy is similar to managing DVT, with a few additional considerations. First, your patient may be hemodynamically unstable, have a large clot, or have other comorbidities.
In these cases, consider hospitalization, and start anticoagulation with either unfractionated or low molecular weight heparin.
The decision on which medication to use depends on whether delivery or other procedures are imminent. Delivery of the fetus should be considered based on maternal and fetal status, as well as the usual obstetric indications, such as gestational age and other antepartum complications.
The key is that having a pulmonary embolism is not, in itself, an indication for immediate delivery, so expectant management is reasonable.
Finally, continue anticoagulation for three to six months, depending on the clinical scenario, ensuring that the entire 6 weeks postpartum is included, because the risk for thrombosis remains elevated in that time.
Alright, as a quick recap… Venous thromboembolism in pregnancy occurs when clots form within the venous system, leading to complications that include deep vein thrombosis and pulmonary embolism.

Review9:44–10:23

Next to history and physical exam, you might need to get a compression ultrasound and chest imaging studies including x-ray, ventilation-perfusion scan, and CT pulmonary angiography.
Management begins with ensuring maternal and fetal stabilization, followed by anticoagulation, usually with low molecular weight heparin, for at least 3 months, ensuring that coverage includes the 6 weeks postpartum.
Venous thromboembolism in pregnancy: Video, Causes | Osmosis