Women who develop hypertension during pregnancy face a higher risk of chronic kidney disease so their blood pressure, heart and kidneys should be monitored after delivering, doctors say.
Starting to have high blood pressure problems while pregnant increases the risk of hypertension, Type 2 diabetes and cardiovascular disease in later life.
An estimated 5 per cent to 10 per cent of pregnancies are affected by hypertensive disorders, previous Canadian and international research suggests. Gestational hypertension – showing blood pressure greater than 140 over 90 mm of mercury – progresses to preeclampsia in 10 to 20 per cent of pregnant women.
Preeclampsia is one of the three leading causes of maternal death worldwide according to the World Health Organization. It's marked by high amounts of protein in the urine as well as sudden spikes in blood pressure.
"We found that women with hypertensive disorders during pregnancy were at higher risk of end-stage renal disease than women without complicated pregnancies," Dr. I-Kuan Wang of China Medical University in Taiwan and co-authors concluded in Monday's issue of the Canadian Medical Association Journal.
The researchers suggested doctors consider close surveillance for small amounts of protein in the urine, known as microalbuminuria, blood pressure and diabetes for women with a history of hypertension disorders in pregnancy.
For the study, researchers analyzed data on 26,651 women in Taiwan with hypertensive disorders in their first pregnancy and compared them with a group of 213,397 women the same age without the disorders.
All of the participants were 19 to 40 years old and did not have a history of hypertension, diabetes or kidney disease when the study began. They were followed for an average of six years.
Women with the blood pressure disorders when pregnant showed a 12.4 times higher risk of end-stage kidney disease – kidney failure requiring dialysis or kidney transplant – compared with those without the disorders, after factors such as other illnesses like coronary artery disease were considered.
Surveillance for heart disease
The mild disorder of gestational hypertension was associated with a 10-fold increased risk of end-stage renal disease.
To put the findings into perspective, almost one in 200 women with hypertension during pregnancy needed dialysis in a relatively short period, Dr. Julian Spaan of Maastrict University noted in a journal commentary accompanying the research.
At an individual level, the absolute risk is relatively low, Dr. Anne-Marie Côté, a nephrologist and expert in maternal medicine at the University of Sherbrooke said in an email from the Kidney Foundation of Canada.
A previous Norweigan study also pointed to an increased risk of end-stage renal disease after hypertension in pregnancy. Finding an association in two ethnic groups in Taiwan and Norway increases the generalizability but it's not clear if the findings can be applied to the Canadian population, Spaan wrote.
"It also highlights one of the current pitfalls of clinical practice: although these women have great attention paid to their high blood pressure during pregnancy, there is no structured follow-up of blood pressure or cardiovascular and renal risk factors after pregnancy," Spaan concluded.
"Better surveillance after pregnancy should help prevent not only chronic kidney disease but also cardiovascular disease."
Côté agreed with call for better surveillance, noting these women are an important group who would be relatively easy to follow with simple laboratory tests of blood and urine.
Whether preventing chronic kidney disease is possible remains to be seen, she added.
The research was funded by National Sciences Council, Executive Yuan, China Medical University Hospital ,Taiwan's Department of Health and the Cancer Research Center of Excellence.