Health researchers have been surprised by the results of a major international study which shows that tightly controlling blood pressure in pregnant women has no harmful effects for their babies.
The international study shows that, contrary to expectations, keeping blood pressure in the normal range with medication does not affect a baby's growth and development in the womb, and there are no differences in outcomes for these babies at birth.
The study, led by BC Women's Hospital and Health Centre and the University of British Columbia in Canada, involved researchers at the University of Adelaide's Robinson Research Institute. The results have been published in the New England Journal of Medicine.
More than 980 pregnant women were involved in the study worldwide, including women from Adelaide.
"For pregnant women whose blood pressure is too high, it places them and their unborn babies at increased risk. The treatment of high blood pressure during pregnancy is extremely important to help avoid complications, such as stroke and death in the mother," says
Professor Bill Hague from the University of Adelaide's Robinson Research Institute.
About half of the participants received blood pressure treatment, usually involving medication, to maintain tight control of their blood pressure within strict limits, while the remainder of the women were allowed to let their blood pressure rise a little, providing it was not to levels that would be dangerous for the woman.
"It was originally thought that blood pressure medication should only be used with caution in pregnant women with high blood pressure, because it would have the potential to impair placental blood flow, with negative impact on the baby’s growth. However, we've been very happily surprised by these results,” Professor Hague says.
"The women whose blood pressure was maintained at normal levels reduced their chances of developing severe high blood pressure, which is associated with an increased risk of stroke and other major complications, and their babies were just as happy and healthy as those whose mums were not on blood pressure medication."
This is the first large high-quality study of its kind looking at the potential impact of blood pressure control in pregnant women with mild to moderate high blood pressure.
"The results of this study have major consequences for the treatment of pregnant women," Professor Hague says. "It helps to reinforce that it's important to do research to get the right balance of what's good for the mum and what’s good for the baby."
He says the message to pregnant women with mild to moderate high blood pressure is: "Talk to your doctor, follow their advice, but don't be afraid to continue with blood pressure treatment because it offers the best benefits to both mum and baby in the immediate term."
Further research is ongoing to see if there is any impact on the children as they develop in later life.