Approximately 1 in every 15,000 pregnant women will develop subarachnoid hemorrhage (SAH) – bleeding in the area between the brain and the thin membranes that cover the brain, according to a study published in the February issue of Anesthesiology.

The researchers found that:

  • the most common risk factor for pregnancy-related SAH is high-blood pressure disorders
  • its incidence is elevated in pregnant women
  • ruptured aneurysms play a less important role in pregnant patients than non-pregnant patients with SHA

Lead researcher Brian T. Bateman, M.D., Massachusetts General Hospital explains:

“When a pregnant patient or new mother has a severe SAH, it’s a particularly tragic event. 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.”

Using data from nearly one-fifth of all U.S. hospital admissions, the researchers have made considerable progress toward the objectives of clarifying the ways in which SAH takes place, defining its risk factors and outcomes, as well as understanding the prevalence of SAH in pregnant women.

Highlights from the Study:

  • Prior investigations on pregnancy-related SHA either did not observe risks linked specifically with pregnancy, or differentiate between aneurysmal or non-aneurysmal SHA. In this study, the researchers found that in pregnant women, aneurysms are the cause of SAH less frequently than in non-pregnant women. This finding highlights the need for investigators to differentiate between aneurysmal and non-aneurysmal cause of SAH. Non-aneurysmal SAH is known to be connected with a better prognosis compared with aneurysmal SAH.
  • The researchers found that hypertensive disease increased the risk of SHA by seven times, and were found in 40% of SAH cases. According to Dr. Bateman, this finding underlines the need for appropriate blood pressure control in vulnerable pregnant patients.
  • Alcohol, tobacco, and drug abuse were the leading potentially modifiable risk factors linked to SHA.
  • Age increased the incidence of SHA. The incident rate for women aged 25 or younger was 3.6 per 100,000 deliveries, while for those aged between 35-44 years the incident rate increased to 11.3 per 100,000 deliveries.
  • Pregnant African American women were 3.3 times and Hispanics 1.4 times more likely to experience SAH than Caucasians, although the factors that caused this disparity are unclear.

Dr. Bateman, said:

“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.”

Written by Grace Rattue