Stroke During Pregnancy

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Stroke has been in the news lately, partly on account of speculation that US President Donald Trump has suffered a series of mini-strokes called trans ischemic attacks (TIAs), or possibly a more substantial stroke. But stroke is also a major health issue, accounting for a large number of deaths and disabilities each year. So you may be wondering about the phenomenon of stroke during pregnancy. A stroke is acute (sudden) loss of function in the central nervous system, due to a problem with a blood vessel. Strokes are classified either as hemorrhagic (a blood vessel has ruptured), or ischemic, meaning that there is a shortage of blood supply to the tissues, due to blood vessel obstruction. Ischemic strokes are further categorized into thrombotic strokes (due to a blood clot, or thrombus, obstructing the vessel in the same place where the thrombus began) and embolic strokes (cerebral embolism).

Pregnant women can suffer different types of strokes. In cases when the stroke is embolic, the heart is the source of emboli that reach the brain, either because of heart surgery, problems with a valve on the left side of the heart (aortic valve and mitral valve), an infection of the inner layer of the heart (endocarditis), an aneurysm in the wall of the heart, or atrial fibrillation ([AF] quivering of the upper chambers of the heart without active pumping of the blood into the ventricles). Such emboli are more likely to form when a person is in a hypercoagulability state, meaning that her blood tends to form clots more easily than it should. Pregnancy is one condition that produces a hypercoagulability state. Cerebral embolism is a particular danger during the post-partum period, from delivery until about two weeks after delivery. Other situations that promote the formation of clots and emboli are circulatory stasis (blood slows down, some of it stopping, in blood vessels) and damage to the inner wall of blood vessels. Together, circulatory stasis, damage to the blood vessel wall, and hyper coagulability of blood are known as the Virchow triad, named for the 19th century Prussian pathologist, Rudulf Virchow.

There have been handful of epidemiological studies, reporting a rates of stroke affecting up to 34 pregnancy women per 100,000 deliveries. Furthermore, the occurrence of strokes during pregnancy has been increasing during the past several years, possibly because older women are having children than previously. Your risk of suffering a stroke depends on a range of risk factors. Emboli that reach the brain also can form in aneurysms and other blood vessel abnormalities (such as entities called arteriovenous malformations) along routes between the heart and brain, plus certain genetic conditions, such as sickle cell disease, entail an elevated risk for clots and emboli. Additionally, in many people, emboli generated on the right side of the heart and in veins (venous thromboembolism) can reach the left side of the heart through what is called a patent foramen ovale (PFO), an opening between the heart’s right and left atria. The foremen ovale that is present in everybody during fetal life and that closes soon after birth, but possibly as many as one third of all people have a PFO. Additionally, there is a severe pregnancy complication called an amniotic fluid embolism (AFE). Although AFE is not only an embolism, because it produces an immune response to amniotic material in the mother’s bloodstream, it can lead to a cerebral embolism.

A stroke can produce temporary or permanent disability and even can be fatal. Disabilities that often occur in strokes include problems with speech or understanding of speech, paralysis of particular parts of the body, such as the face, arms, or legs. Typically, one side of the body or face is affected.

In cases of stroke, medications are given to restore blood flow to the affected area of the brain and to prevent additional emboli from forming and reaching the brain. Quick recognition of the stroke is extremely important and is a major factoring in determining the treatment. The gold standard treatment consists of drugs of a category called fibrinolytic (or thrombolytic) agents, which are given to break up the clot. In particular, a clot busting agent called tissue plasminogen activator (tPA) is given, but it is effective only if you receive it within approximately 4.5 hours of the onset of the stroke. The drug can be given intravenously, or endovascularly, meaning through an instrument in a catheter that is inserted into a vein. Although tPA is considered to be a risk for the fetus, it has been administered successfully in pregnancy and the risk must be weighed against the risks and benefits of giving the drug and the risk of not giving it.

In cases of hemorrhagic stroke, there are cases in which surgery needed to relieve pressure building on the brain as a result of bleeding, and sometimes also for blood vessel repair. In cases of ischemic stroke and emboli, this goal is achieved using blood thinner medications, such as warfarin (and newer drugs that have similar functions) or heparin and antiplatelet therapy, such as aspirin. The danger of warfarin is a huge issue in pregnancy, but it’s a complex issue, because warfarin is dangerous to the baby only at particular times during pregnancy and often is the drug of choice when the mother has a very severe clotting problem. Sometimes it is best to avoid warfarin for the entire pregnancy while giving the mother low molecular weight heparin (LMWH) or ultrafractionated heparin (UFH). Other times, doctors prefer to avoid heparin during the first trimester, then resume warfarin in the second trimester, and then switch back to heparin in the last weeks of pregnancy. Aspirin, which also reduces clotting but by inhibiting the clotting cells called platelets is useful in certain cases, and is safe for most of pregnancy.

While clot busting medications such as tPA are effective if given within 4.5 hours of the onset of ischemic stroke symptoms, researchers are investigating whether and how endovascular delivery of the drugs can improve the effectiveness. A procedure known as mechanical thrombectomy, in which endovascular techniques are used to remove the clot from the blood vessel, can be effective up to 24 hours after the stroke symptoms have begun. Additionally, some stroke centers have the capability to cool down your body, and especially your brain, ever more rapidly. Known as therapeutic hypothermia, this procedure is showing effectiveness in improving stroke recovery, but generally it is performed only by specialized groups of doctors who are researching it (this is likely to change in the years to come). As with the other treatments, hypothermia must be initiated very early.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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