Pregnancy causes many changes in your body, from belly to blood.
In fact, pregnant women are five times more likely to develop blood clots than non-pregnant patients because during pregnancy, the body increases production of blood factors that promote normal clotting. The growing uterus also impedes return of blood in veins in the lower part of the body. Most of the time, these changes result in superficial problems like varicose veins.
Sometimes, increases in clotting factors along with decreased flow in the veins from the expanding uterus can cause blood clots to develop in the legs. When a clot breaks free and travels to the lungs, it becomes a medical emergency known as pulmonary embolism (PE).
PE is rare, affecting approximately 1 in 7,000 pregnancies, according to Williams Obstetrics 25th edition. However, PE accounts for approximately 11% of maternal deaths. Nearly two-thirds of pregnancy-related deaths due to PE occurred after delivery.
If PE symptoms are addressed immediately, effective treatment is available. Tennis legend Serena Williams suffered blood clots in the legs after giving birth to her daughter in 2018. Williams, who had a history of PE, recognized her symptoms – which can include shortness of breath and a cough that may include blood – and advocated for herself to receive anti-clotting medication that stopped the clots from reaching her lungs.
However, PE does not always cause recognizable symptoms. Such was the case for Instagram influencer Emily Mitchell who, days before Christmas 2020, collapsed with a fatal PE while pregnant with her fifth child.
There is no way to say for certain who may develop PE, so it's important for all pregnant patients – and moms who recently delivered – to know the symptoms. Let's discuss what to look for, who might be at increased risk, and which treatment options are available.
Possible symptoms of pulmonary embolism
The most common symptoms of PE are shortness of breath and a cough that may include bloody sputum. Especially during flu season and the ongoing COVID-19 pandemic, even a little cough warrants being checked out.
Some patients may experience these symptoms during pregnancy or in the weeks after delivery:
- Dizziness, fainting, or lightheadedness
- Increased heart rate
- Pain or swelling that is more noticeable in one leg
- Unexplained anxiety
Large blood clots can significantly reduce oxygen supply to the lungs, leading to organ damage. In extreme cases, large clots can block both lungs, causing total cardiovascular collapse.
Who might be most at risk
Patients with a personal or family history of blood clots or PE are at increased risk of developing PE during pregnancy. This includes thrombophilia, a rare genetic condition that causes an imbalance in the blood that increases the risk of clotting.
Being 35 or older during pregnancy can also increase the risk, as can having a personal history of these risk factors:
- Bone, brain, or joint surgery
- Excess weight or obesity
- Heart disease
- Inflammatory conditions
- Long-term immobility, such as paraplegia or extended bed rest
- Pancreatic, ovarian, or lung cancer
- Past cesarean section (C-section)
- Sedentary lifestyle
- Sickle-cell disease
If you know you have a family or personal history of PE, you may still be able to have a safe, healthy pregnancy. Talk with your Ob/Gyn about your health history.
To diagnose PE, we use ultrasounds, CT angiography, and X-ray imaging. These tests help us find blood clots either in the lower legs or in the lungs. Some types of imaging delivers a small dose of radiation, at a level too low to harm the pregnancy. These tests can be lifesaving, and we encourage you to ask questions if you are concerned.
Preventing and treating PE
While we cannot prevent 100% of clots, you can reduce your risk by following a few tips. The most important is to stay active. Very few women should not be walking around either before delivery or immediately after having a baby. I have taken care of women who are told that the best thing is to stay in bed for a week after having a baby. That’s not true – and can increase your risk of developing blood clots.
After a C-section, you won't be moving around too much right away. So, we place your legs in special boots called sequential compression devices. This advanced legwear acts like high-powered compression stockings to gently squeeze the calves and keep your blood moving. The sensation is painless, though some women are annoyed by having to sit still to wear them. The short-term inconvenience can help reduce your risk of a potentially life-threatening blood clot.
If you have a history of PE, your doctor may recommend taking a low dose of heparin, a blood thinner shown to be safe during pregnancy. Unlike warfarin, heparin does not cross the placenta and has not been shown to cause fetal complications. Your doctor may recommend that you continue taking heparin for up to three months after delivery to further reduce your risk.
Successful treatment requires quick recognition of symptoms and emergency medical intervention. Large and life-threatening clots may be removed or broken up through a procedure to extract the clot or inject it with dissolving medication. Some clots may be treated with blood thinners only. Filters may be placed to prevent clots in the legs from traveling to the lungs.
Anytime you start to feel "different" or unwell during pregnancy or in the weeks after delivery, contact your Ob/Gyn. You will never "be a bother" – we want to hear from you to check out your symptoms.