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An aneurysm is a widening of a blood vessel. It can take the form of a ballooning, a bulge, or other distensions that cause the diameter of the blood vessel to be larger than in should be. This happens, due to a weakened vessel wall being stretched over time by the pressure of the blood. Aneurysms can occur both in arteries and veins, but venous aneurysms are quite rare, so usually when somebody refers to an aneurysm it is an arterial aneurysm, a fairly common condition. Today, we’ll focus on cerebral aneurysm, also called an intracranial aneurysm, an aneurysm that occurs within the brain. This is one of the most common categories of aneurysms and one of the main type aneurysm concerns in the setting of pregnancy.
While aneurysms are thought to be fairly common in adults of all ages, and thus during pregnancy, it is difficult to estimate the actual prevalence of this blood vessel abnormality. This is because most aneurysms are thought not to produce any symptoms. Often, they are present simply as a slight, asymptomatic (symptom-free) swelling of an artery that never gets noticed, unless the region of the body where the aneurysm is located gets imaged as part of an evaluation of some other problem. Otherwise, aneurysms are discovered, when they produce symptoms, as happens if they are pushing on something.
Cerebral aneurysms are a particular concern during pregnancy, because these malformations occur much more often in women than in men. The opposite gender association is true for aortic aneurysms, aneurysms of the aorta, the large artery that carries blood from the heart’s left ventricle to arteries that carry it through body tissues. Factors that increase your risk of suffering an aneurysm include high blood pressure (hypertension), smoking (which damages the walls of blood vessel and also raises blood pressure), atherosclerosis (a disease of the walls of arteries), and certain genetic conditions of connective tissue, such as Ehlers-Danlos syndrome and Marfan syndrome. Additionally, a genetic condition called autosomal dominant polycystic kidney disease is associated with elevated risk of cerebral aneurysm. Because a great but unknown number of people are thought to harbor asymptomatic aneurysms, it is also hard to compute the percentage of aneurysms that actually produce problems, such as the aneurysm rupturing.
Whether you are pregnant or not, cerebral aneurysm is diagnosed using CT angiography, magnetic resonance (MR) angiography, or cerebral angiography. Of these imaging techniques, doctors prefer to use magnetic resonance during pregnancy, because the other types expose you to some ionizing radiation, although it is focused on your head and nowhere near the womb.
As for the consequences of a cerebral aneurysm, as mentioned earlier, most of these blood vessel abnormalities go unnoticed. However, there is some concern that changes in the body that occur during pregnancy may cause a small aneurysm to grow. Complications that can occur from aneurysms growing include putting pressure on nearby structures within the brain and triggering the formation of blood clots. An even greater concern is that an aneurysm will rupture, causing hemorrhage (bleeding) within the brain. In particular rupture of a cerebral aneurysm leads to what doctors call a subarachnoid hemorrhage (SAH), which threatens life. If a cerebral aneurysm ruptures, it threatens the mother’s life, along with the life of the fetus.
A lot of controversy surrounds the evaluation of risk that an aneurysm will rupture. However, the are a handful of known risk factors, which are:
- Large size of the aneurysm. In the brain, an aneurysm less than 5 millimeters is thought to be a lower risk, although some controversy surrounds this idea
- High blood pressure
- Presence of daughter aneurysms, meaning aneurysms that balloon out from other aneurysms
- Various other features of aneurysm shape
- Location of the aneurysm in the posterior (back region) of the brain rather than the anterior region
Management of cerebral aneurysm includes medications to lower blood pressure and to prevent the aneurysm from growing. The main blood pressure medications that are considered very safe during pregnancy, and also during breastfeeding, are called beta blockers.
Certain aneurysms are considered to put the mother at high risk, either because of their size or because of other factors. Such aneurysms require invasive treatment in the form of either open surgical procedures (neurosurgeons go through the skull), or endovascular treatment. In the endovascular strategy, the aneurysm is treated with instruments inserted through tubes in the blood vessels. In the case of cerebral aneurysm, treated with brain surgery, neurosurgeons can “clip” the aneurism, meaning that little clamps are applied that close of the entrance into the aneurism from the blood vessel. Alternatively, in an endovascular procedure, doctors can use coils to block blood from entering the aneurysm. With some of the hardware that is inserted, such as the clips, there is some concern than they will be affected if you later get magnetic resonance imaging (MRI), even with clips made from titanium which is much less magnetic than iron-based materials, but still is slightly magnetic. Consequently, it is recommended that all imaging be performed in the same medical center where the clipping has been performed, so that all of the details are known and coordinated.