Rate of high blood pressure disorders in pregnancy on the rise, study suggests

The rate of high blood pressure disorders in pregnancy has risen over the last decade in Canada, a new study suggests.  

The research, published Monday in the Canadian Medical Association Journal, found that rates of hypertension and pre-eclampsia increased by 40 per cent between 2012 and 2021.

“Blood pressure remains a cornerstone of maternal health monitoring during pregnancy,” senior author Dr. Joel Ray, who is also a clinician-scientist in obstetrical medicine at St. Michael's Hospital in Toronto, said in an interview.

High blood pressure — also called hypertension — during pregnancy is dangerous for both the mother and fetus, but can be identified with regular monitoring and can be prevented in many cases with low-dose Aspirin in women identified as being at risk, Ray said.

In addition, there are highly effective blood pressure medications that are "definitively safe" to take during pregnancy, he said.  

Although the study did not determine the causes of the increasing rates of high blood pressure among pregnant women, it noted that "risk factors for (hypertensive disorders of pregnancy) are on the rise, including obesity, pre-pregnancy diabetes mellitus and advanced maternal age." 

But to Ray, the causes aren't as important as being aware that this is a growing problem that requires treatment, he said. 

“We just need to be more on the ball with identifying it and getting women on the blood pressure-lowering medications that they should be on, in addition to the Aspirin prevention,” he said. 

The frequency of blood pressure monitoring during pregnancy can be improved by encouraging women to regularly use blood pressure monitors in pharmacies or get at-home kits if that's financially feasible, and discuss those readings with their health-care providers, Ray said.  

The researchers looked at records for more than 2.8 million hospital deliveries between 2012 and 2021 across Canada, except for Quebec. 

They found the rate of high blood pressure disorders increased from 6.1 per cent to 8.5 per cent of those pregnancies in that time period. 

One area this study didn't examine, but that warrants more research, is the rate of high blood pressure disorders post-partum, Ray said. 

Women can also develop those disorders in the days following delivery, but may not get the care they need because follow-up obstetrical appointments aren't scheduled until six weeks after birth, he said. 

Dr. Catherine Varner, a deputy editor for the Canadian Medical Association Journal and a Toronto emergency department physician, wrote an editorial about the study calling for more access to obstetrical care — especially in the days and weeks following birth when women aren't closely monitored — through teams of midwives, family physicians and specialists.

”I think this study is yet another indicator that people are entering their reproductive lives with more health problems than the generation did before. And our health-care systems are not prepared for that,” Varner said in an interview.

"People who have hypertensive disorders in pregnancy have a particularly high need of close monitoring in the immediate post-partum, the early post-partum period, and sometimes they don't have a good place to follow up to have their blood pressure checked," she said. 

Even if post-partum women are checking their own blood pressure with a home monitor or at a pharmacy, they often don't have a family doctor or other outpatient provider to turn to if their blood pressure is high, Varner said. 

"They come into the emergency department sort of (as) a last resort,” she said. 

This report by The Canadian Press was first published July 29, 2024. 

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