Large Study Helps to Define Risk Factors for Pregnancy-Related Subarachnoid Hemorrhage, a Leading Cause of Maternal Mortality

A large study published in the February issue of Anesthesiology found that the devastating complication of subarachnoid hemorrhage (SAH) occurs in approximately 1/15,000 pregnancies, that high-blood pressure disorders are the most common risk factor for pregnancy-related SAH, and that contrary to SAH in non-pregnant patients, ruptured aneurysms play a less important role in the pregnant patient.

SAH occurs when blood leaks between delicate membranes that surround the brain (but not in the brain itself). Its incidence is known to be elevated in pregnant women.

“When a pregnant patient or new mother has a severe SAH, it’s a particularly tragic event,” said lead study author Brian T. Bateman, M.D., Massachusetts General Hospital. “Despite this, relatively little is known about the causes of SAH during pregnancy and how that differs from the causes of SAH outside of pregnancy.”

Dr. Bateman said that he and his research team made significant progress toward the objectives of understanding how frequently pregnancy-related SAH occurs, defining its risk factors and outcomes, and clarifying the ways in which SAH takes place. The study utilized data from nearly one-fifth of all U.S. hospital admissions.

Study Highlights:

• Previous studies on SAH during pregnancy either did not differentiate between aneurysmal or non-aneurysmal SAH, or did not observe risks associated specifically with pregnancy. The current study found that in pregnant women, aneurysms are the cause of SAH less frequently than in non-pregnant patients, underscoring the need for researchers to make a distinction between aneurysmal and non-aneurysmal causes of SAH. Non-aneurysmal SAH is known to be associated with a better prognosis than aneurysmal SAH. 
• Hypertensive diseases were found in 40 percent of SAH cases and increased the risk of SAH seven-fold. Dr. Bateman said this finding emphasizes the need for appropriate blood pressure control in vulnerable pregnant patients.
• Pregnant Black women were 3.3 times and Hispanics 1.4 times more likely to experience SAH than Caucasians, though it was unclear what factors caused this disparity.
• Incidence of SAH increased with age. For women 25 years or less, the incident rate was 3.6 per 100,000 deliveries.  For women 35-44 years, it was 11.3 per 100,000 deliveries.  
• Tobacco, drug, and alcohol abuse were the leading potentially modifiable risk factors associated with SAH.

“Understanding the risk factors that predispose pregnant patients to SAH, the clinical presentation, and the distinction from more benign forms of headache may help clinicians identify these patients so that appropriate work-up and therapy can be performed,” said Dr. Bateman. 

For more information, visit the Anesthesiology website at www.anesthesiology.org.