Study recommends normalizing blood pressure in pregnant women

Throughout her career in Canada and the UK, Dr. Laura Magee has taken a restrained approach to use of blood pressure-lowering medication in her pregnant patients, fearing that lowering pressure could reduce the flow of blood and vital nutrients to their babies.

But Magee, a researcher at the Child & Family Research Institute (CFRI) and the University of British Columbia (UBC), and a physician at BC Women's Hospital and Health Centre, an agency of the Provincial Health Services Authority (PHSA), has up-ended her own beliefs with an international study being published today in the New England Journal of Medicine.

The 15-country study shows that treating a woman's elevated blood pressure during pregnancy is safer for her, and safe for her baby. As a result of these findings, Magee and her collaborators recommend normalizing blood pressure in pregnant women.

"Before this study, I was a 'less tight' controller," Magee says. "I was hoping that this approach would be better for the baby, without increasing risks for the mother. However, I was wrong. 'Less tight' control, which means allowing blood pressure to be mildly to moderately elevated in pregnancy, is not better for the baby. It's actually harmful to the mother, who will more often experience levels of blood pressure that increase the risk of stroke. As a responsible maternity care provider, I can no longer justify a 'less tight' approach to blood pressure control."

The study, which tracked the health of 987 women and their newborns at 94 sites around the world, addresses an age-old belief that reducing elevated blood pressure during pregnancy might lead to reduced growth in the womb and worse health at birth.

But normalizing a pregnant women's elevated blood pressure did not result in poorer outcomes for babies before or after birth. At the same time, allowing the mother's blood pressure to be mildly to moderately elevated in pregnancy led to more episodes of dangerously elevated blood pressure that increase the risk of stroke and death for the mother during pregnancy.