Pregnant women with whose blood pressure is even slightly raised can be dramatically more at risk of developing diabetes or heart disease, say scientists.
In the first study of its kind a condition called pre-hypertension – where blood pressure is in the upper range of normal – has been shown to be potentially dangerous.
Up to one-in-seven expectant mothers in the UK already suffer high blood pressure and the discovery could lead to many more requiring monitoring.
Professor Jian-Min Niu, of Guangdong Women and Children Hospital in China, said: “Our findings underscore an important issue that has been long ignored in clinical practice – the fact criteria for hypertension in pregnancy are derived from the general population.
“We anticipate if reaffirmed in further research, our study could spark a change in what we currently deem healthy blood pressure in pregnant women.”
The research found pregnant women whose blood pressure is in the upper ranges of normal could be at high risk of developing metabolic syndrome – a combination of diabetes, hypertension and obesity – and heart disease risk after giving birth.
Current guidelines do not distinguish between pregnant women and the general population and define hypertension as persistently elevated blood pressure that is 140 millimeters of mercury (mm Hg) systolic or 90 mm Hg diastolic and above.
Readings of 120-139 mm Hg systolic over 80-89 mm Hg diastolic is deemed ‘pre-hypertension’ – a warning sign of high blood pressure in the future.
But the study published in Hypertension said pregnant women with blood pressure in this range had 6.5 times greater odds of developing metabolic syndrome compared to those in the lower normal range.
It looked at 507 Chinese women with uncomplicated pregnancies, no history of hypertension and normal blood sugar and cholesterol who underwent seven or more blood pressure measurements along with other standard tests including weight
measurements and foetal ultrasounds.
Blood sugar and cholesterol levels were also tested at the start, shortly before and after giving birth and once every few months for up to 1.6 years after giving
The participants were grouped into three categories including those whose blood pressure remained on the lower end of normal (34%), around the mid-point (52%) or in the pre-hypertension range (13%).
A series of snapshot measurements did not predict future risk but patterns of repeated elevations did – highlighting the dynamic nature of blood pressure during pregnancy.
The results support the idea of pregnancy as a cardiovascular stress test for women that can reveal underlying disturbances in blood pressure regulation, glucose and cholesterol metabolism.
Abnormalities in all three areas can disrupt functions and lead to full-blown cardiovascular disease years down the road.
Prof Niu said globally the burden of cardio-metabolic diseases in women has been
rising steadily over the last decades.
He said: “Blood pressure measurements are already done as matter of routine and
cost-effective checkups during pregnancy so our findings underscore this tool’s potential to gauge a woman’s post-partum cardiovascular risk.
“Early identification of metabolic risk factors and implementation of lifestyle modifications may help delay the onset of cardiovascular disease that would present itself 20 to 30 years after delivery.”