Pulmonary embolism during pregnancy

Typical symptoms of pulmonary embolism include the following:

• Sudden, extreme difficulty breathing
• Chest pain
• Coughing, especially if the person coughs up blood or has other pulmonary embolism symptoms too
• Feeling dizzy or faint, or unconsciousness
• Rapid heartbeat

Sometimes the symptoms are only mild, like shortness of breath or a swollen leg due to thrombosis. It is difficult to tell these apart from typical effects of pregnancy.

The likelihood of pulmonary embolism is higher in people who:

• have had it or thrombosis before
• had complications in a previous pregnancy
• have heart, kidney or inflammatory bowel disease
• are overweight

The usual series of tests for pulmonary embolism are also used in pregnant women. Doctors try to avoid using imaging techniques that cause radiation exposure – unless there is very good reason to believe that the woman could have pulmonary embolism.

It is harder to interpret the test results when the patient is pregnant. A common test is the D-dimer test. It reacts to substances that are released when blood clots are broken down. Particularly in the final trimester of pregnancy, the test might deliver an abnormal result even though the woman doesn’t have pulmonary embolism. This is because the substances that the test reacts to are produced during pregnancy too.

If imaging is needed, the doctors will choose a type that involves as little radiation exposure as possible. Experts believe that these imaging techniques aren't harmful to the unborn child. They are carried out in the chest area, and the womb is lower down, so it’s unlikely to be exposed much at all.

It is also possible to do an ultrasound scan (sonogram) of the leg to check for thrombosis. This scan doesn’t use any radiation at all. But more examinations may be needed, depending on the results.

Pulmonary embolism is treated with medication to prevent blood-clotting (anticoagulants). Heparin is a suitable option for pregnant women because it’s not passed on to the child through the placenta. A low-molecular-weight heparin (LMWH) is typically used rather than an unfractionated heparin (UFH) because it’s easier to predict the effects of LMWH. LMWH is also less likely to have side effects.

Pregnant women are normally given a form of heparin that’s injected under the skin (subcutaneously). With a little practice, they can inject it themselves.

Heparin shots are usually injected into the thigh or lower belly. You pinch the skin to form a fold and then insert the fine needle using the other hand. That doesn’t hurt the baby, but the woman might feel a little pain. This is nothing to worry about – the pain is caused by the heparin. There may also be bruising where the needle went in.

If the woman's blood pressure and circulation is stable, and the treatment is effective, pulmonary embolism doesn’t have any direct effects on the unborn child.

As the due date approaches, it’s important to prepare well. Heparin makes bleeding more likely, so there's a risk of heavier bleeding during the birth. To prevent that from happening, the heparin treatment is stopped shortly before the birth (just a few hours, if possible). The easiest way to do this is to start (induce) the labor process at a planned time.

You can ask your doctor about the pros and cons of planning the birth like this, and whether inducing labor is an option for you. The best thing is to have a multidisciplinary team around you to help make the right decision for you.

You start taking the anticoagulants again shortly after giving birth, and keep on taking them for several weeks.

Heparin doesn’t get into breast milk, which means you can use it while breastfeeding too. But you can also change to a different anticoagulant after you’ve given birth. One possibility is warfarin, which is a type of drug known as a vitamin K antagonist. People who take warfarin when breastfeeding are advised to give their baby vitamin K. The warfarin that gets into breast milk has no effect, but giving the child vitamin K ensures its blood is definitely still able to clot.

Other anticoagulants are only sometimes suitable for people who have just given birth. Fondaparinux and direct oral anticoagulants (DOACs) might build up in your milk. So they’re only an option for women who aren’t breastfeeding.

Experts recommend taking heparin during future pregnancies too, as a preventive measure to reduce the risk of having another embolism.

In rare cases, the blood pressure and circulation of people with pulmonary embolism become unstable. Then there’s a risk of heart failure. This is a medical emergency, requiring intensive care and close monitoring of the mother and unborn child. The usual response is to give the mother a fast-acting shot of high-molecular-weight heparin or unfractionated heparin (UFH). The medical staff do regular checks to monitor how quickly the blood clots. Then they can adjust the dosage if necessary.

In most cases, the pregnant person is also given fluid, oxygen and medications to stabilize their blood circulation. The doctors will check whether procedures like thrombolysis, right-heart catheterization or thrombectomy are suitable for breaking up or removing the clot.