High blood pressure during pregnancy could elevate risk of future stroke

"We've found that women who had high blood pressure during pregnancy could be at higher risk of stroke, particularly if they had pre-eclampsia, which is a more severe form of high blood pressure," says Dr. Aravind Ganesh, a neurology resident at the University of Calgary. "The elevated risk of stroke could be as high as 40 per cent."

Dr. Ganesh, along with Neha Sarna (medical student), Dr. Rahul Mehta (internal medicine resident) and senior author Dr. Eric Smith (stroke neurologist), conducted a systematic review -- basically, a study of studies.

Nine studies specifically looked at hypertension (high blood pressure) during pregnancy and its relationship to future risk of stroke.

The studies followed women for anywhere from one to 32 years after a pregnancy, and found consistent evidence that those with a history of hypertension in pregnancy are more likely to experience stroke in later life.

Hypertension is the most common medical problem encountered during pregnancy, complicating two to three per cent of all pregnancies. It can pose many risks, such as a decrease in blood flow to the placenta or early delivery.

Women are closely monitored throughout pregnancy for changes in blood pressure, but there are currently no specific recommendations regarding stroke-related screening or preventive measures post-partum.

"These women should be more closely followed for a re-emergence of hypertension, as well as for cholesterol, diabetes or other markers of increased risk of stroke," says Dr. Ganesh.

The exact cause of hypertension during pregnancy is undetermined, but one theory is that some women are genetically predisposed to high blood pressure and the pregnancy brings it on. Even though it might return to normal post-partum, these women need to monitor their blood pressure and to reduce their risk of having a stroke later on.

"Hypertension is the most important risk factor for stroke," says Dr. Michael Hill, co-chair of the Canadian Stroke Congress. "Knowing your blood pressure may be one of the most important steps you can take to reducing stroke risk, something that is particularly true among women with a history of pregnancy-associated hypertension."

"It's important for women to be aware of their blood pressure, and potential changes to it, during pregnancy," says Ian Joiner, director of stroke at the Heart and Stroke Foundation.

"An increase is an indication that they should to talk to their doctor about their risk factors and overall vascular health. The bottom line is that it's important that women with pregnancy-related hypertension routinely monitor their blood pressure throughout their lives."