Extreme hypertension in pregnancy tied to kidney disease

Women who develop preeclampsia, a form of dangerously high blood pressure during pregnancy, are five times more likely to develop end-stage kidney disease later in life than women who have normal blood pressure during pregnancy, a Swedish study suggests. 

Preeclampsia has long been linked to an increased risk of events like heart attacks and strokes years later, and some previous research also suggest that this form of high blood pressure might also be one reason why women are more likely to develop advanced kidney disease than men. 

For the current study, researchers examined data on almost 2.67 million births among 1.37 million women between 1982 and 2012. A total of 67,273 women, or 4.9 per cent, developed preeclampsia during at least one pregnancy, and 410 women developed end-stage kidney disease. 

Women who had preeclampsia in two pregnancies were more than seven times more likely to develop end-stage kidney disease than mothers who never had preeclampsia, the study found. 

“This study shows that pre-eclampsia is a sex-specific, independent risk factor for the subsequent development of end-stage kidney disease,” said lead study author Ali Khashan, a public health researcher at University College Cork in Ireland. 

“However, the overall end-stage kidney disease risk remains small, and women with a history of preeclampsia should not be overly concerned,” Khashan said by e-mail. 

Women who develop preeclampsia earlier in pregnancy — before the halfway point — are more than nine times more likely to develop end-stage kidney disease than mothers with normal blood pressure during pregnancy. 

The challenge with preeclampsia is that women often don’t experience symptoms until they have a life-threatening problem, especially when they’re otherwise healthy and have uncomplicated pregnancies. 

Kidney failure, also called end-stage kidney disease, is most commonly caused by diabetes or high blood pressure. Other causes can include autoimmune diseases and genetic disorders or chronic urinary tract problems. 

With kidney failure, people require an organ transplant or dialysis. 

The connection between preeclampsia and kidney failure in the study persisted even after researchers accounted for other factors that can impact maternal health like age, education, and pre-pregnancy health problems like existing kidney disease or cardiovascular disease. 

Women in the study who had preeclampsia were older on average and had a higher body mass index. 

Among women with no preeclampsia in the first pregnancy, 14.2 per cent were overweight and 4.9 per cent were obese. Among women who did develop preeclampsia in their first pregnancy, 20.1 per cent were overweight and 11.8 per cent were obese.

The study wasn’t a controlled experiment designed to prove whether or how preeclampsia might lead to kidney failure later in life.

It’s possible that risk factors like obesity, high blood pressure, and diabetes contribute to both preeclampsia and kidney failure down the line, researchers note in PLoS Medicine. It’s also possible that some women who had preeclampsia might have had undiagnosed kidney problems at the time.

“We were able to account for maternal obesity and comorbidities such as diabetes, and the reported results are independent of these factors,” Khashan said. “However, these factors cannot be ruled out completely as potential mediators between preeclampsia and end stage kidney disease.”

By Lisa Rapaport