New research suggests links between pregnancy, childbirth and future maternal risk of hypertension

High blood pressure (hypertension) is a leading modifiable risk factor for cardiovascular disease, according to Statistics Canada. But because high blood pressure often has no symptoms, many people do not know they are at risk until serious health complications occur.

New research from the Libin Cardiovascular Institute suggests that a woman’s reproductive history may be an important factor to consider when assessing future cardiovascular risk.

This is an area of interest for Dr. Nabilah Gulamhusein, PhD'25, a medical student at the Cumming School of Medicine (CSM) who recently completed her doctorate under the supervision of Dr. Sofia Ahmed, MD, a CSM adjunct professor.

As part of her PhD research, Gulamhusein investigated the relationship between pregnancy, childbirth and blood pressure. Her work, recently published in npj Cardiovascular Health, analyzed data from multiple studies and found that people who have given birth are at a higher risk of developing hypertension later in life when compared to those who have never given birth. 

She also found the number of births matter. 

“We looked at people who had given birth once, twice, three times and four or more times and found that there is a graded relationship between number of child births and risk of hypertension,” says Gulamhusein.

The findings are significant because, while previous studies have explored the relationship between pregnancy and blood pressure, results have been inconsistent. Gulamhusein’s meta-analysis was one of the first to bring the available evidence together to better understand this connection.

Although more research is needed to determine why childbirth impacts future maternal hypertension risk, Gulamhusein theorizes that the relationship is complex. It may involve the physiological changes that occur during pregnancy and after giving birth, as well as the demands associated with raising children.

For Gulamhusein, the most important message is that knowledge is power. 

“Knowing that the risk of hypertension may increase with childbirth facilitates informed decision making,” she says. 

Ahmed agrees and says that understanding personal risk factors — including reproductive history — can help support earlier detection, prevention and better cardiovascular health for women.

“There is increasing recognition that female sex-specific factors provide important insights into cardiovascular and kidney health,” she says. “Pregnancy is very common and understanding how this important life event affects the risk of hypertension will help guide strategies to optimize overall cardiovascular and kidney health across the lifespan.”