Pregnancy and Stroke Risk in Women

Jessica Tate; Cheryl Bushnell

Disclosures

Women's Health. 2011;7(3):363-374. 

In This Article

Risk Factors for Pregnancy-related Stroke & CVT

Young pregnant women may have risk factors that are typically associated with stroke in the general population, especially with the increasing prevalence of obesity at younger ages. Some of these risk factors associated with pregnancy-related stroke include hypertension, diabetes, valvular heart disease, hypercoagulable disorders, sickle cell disease, lupus, abuse of tobacco and other substances, and migraines.[4,5] Hypertension in pregnancy may be pre-existing, gestational, or associated with preeclampsia or eclampsia. Compared with women without hypertension, women with hypertension complicating pregnancy are six- to nine-fold more likely to have stroke.[3,5] Complications of pregnancy, labor and delivery have also been associated with increased risk of stroke, including hyperemesis gravidarum, anemia, thrombocytopenia, postpartum hemorrhage, transfusion, fluid, electrolyte and acid-base disorders, and infection.[4,5] Cesarean delivery has been associated with peripartum stroke, although a causal relationship has not been well established.[2,4] The association may reflect a higher likelihood for physicians to recommend cesarean delivery in women who suffer strokes during pregnancy. Historically, cesarean delivery has been advocated for women with ICH, particularly recent subarachnoid hemorrhage, untreated ruptured arteriovenous malformation (AVM) or unclipped ruptured aneurysm, to avoid potential risks during labor and delivery.[2] However, studies suggest that outcomes of vaginal and cesarean delivery are probably equivalent after ICH.[18,19] On the other hand, cesarean delivery may actually be a risk factor for postpartum stroke due to CVT. Normal physiologic changes during pregnancy, including resistance to activated Protein C and a decrease in functional Protein S, compounded by the transient hypercoagulability associated with surgery, may lead to clot formation.[4] Finally, age greater than 35 years increased the odds of stroke twofold, and African–American race-ethnicity increased the odds of stroke by 1.5-fold.[5] Similar results were reported in an analysis of pregnancy-related ICH alone.[7]

Potential causes of stroke identified in the literature include those that can occur in the young nonpregnant population, and those that are exclusive to pregnancy. Diagnoses that are not specific to pregnancy include venous sinus thrombosis, cardioembolism, CNS or systemic vasculitis. Those that are more specific complications of pregnancy include preeclampsia/eclampsia, amniotic fluid embolism and postpartum angiopathy.[1,8,11,12,20] Postpartum cardiomyopathy can result in cardioembolism, or less commonly, watershed infarction from hypotension.

Although CVT occurs due to thrombosis of the sinuses, cerebral veins or jugular veins, and ischemic stroke occurs as a result of an arterial thrombosis or hemodynamic cause, there is quite a bit of overlap in the risk factors for both types of strokes during pregnancy. The primary causes for both types of strokes are thought to be influenced by the prothrombotic state of pregnancy itself, often in the setting of dehydration or an underlying predisposition for thrombophilia.[13] The causes and risk factors for CVT and thrombophilias have been extensively reviewed and published recently.[13] The physiologic changes during pregnancy that may lead to arterial or venous thromboembolism include decreases in circulating antithrombotic factors, venous stasis or sudden reduction in blood volume after delivery.[18] Identifiable etiologies of stroke in the population-based studies previously cited are summarized in Table 2.

Several studies have found that preeclampsia/eclampsia and underlying cerebrovascular malformations were the most common identifiable causes of pregnancy-related ICH (Table 3).[1,7,8,11,12,20] Preeclampsia/eclampsia is a cause of reversible posterior leukoencephalopathy syndrome, which can be associated with reversible vasogenic edema, typically in the posterior portion of the brain, as well as ICH, presumably due to the abnormalities in autoregulation.[21] In addition, preeclampsia/eclampsia has been associated with the spectrum of reversible cerebral vasoconstriction syndromes, which is a clinical syndrome consisting of thunderclap headache with or without focal neurologic deficits, and reversible arterial segmental vasoconstriction.[10] These two reversible syndromes are most likely under-recognized and under-diagnosed because the primary manifestation may be headache plus visual scotomata, representing severe preeclampsia, and the most important priority is delivery of the infant, rather than diagnostic imaging.[22]

There are several factors that may increase the risk of AVM or aneurysmal rupture during pregnancy, such as increased blood volume and cardiac output, and structural changes in the vascular wall.[18] However, whether pregnancy truly increases risk of rupture is a topic of ongoing debate. Bateman et al. found that the rate of hemorrhage attributable to cerebrovascular malformations was similar in pregnant and nonpregnant women, at 0.50 and 0.33 per 100,00 person-years, respectively.[7] Additional etiologies in pregnancy include metastatic choriocarcinoma, and abuse of other substances, including alcohol and methamphetamines.[19,23]

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