Although they were prescribed widely in the 1960s to women looking to avoid dangerously high blood pressure during pregnancy, diuretic drugs should not be recommended as a way to prevent this serious condition, called preeclampsia, according to a recent review of studies.
Women who took diuretics -- commonly known as "water pills" -- during pregnancy were not any less likely to develop preeclampsia, to deliver prematurely or to lose their babies than those who did not take the pills, said obstetrician David Churchill of New Cross Hospital in West Midlands, England, and colleagues.
However, women who took diuretics were significantly more likely to have nausea and vomiting.
"From this review, no clear benefits have been found from the use of diuretics to prevent preeclampsia," Churchill said.
The review included five studies and 1,836 women.
The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Women with preeclampsia, usually diagnosed after 20 weeks of pregnancy, have high blood pressure and protein in their urine. The condition can be dangerous for both mother and fetus, causing pregnancy complications, early delivery and even death.
"Currently, the only cure for the disease is delivery of the baby and the placenta, but this leads to many babies being born prematurely and vulnerable," Churchill said.
For this reason, doctors have focused on diet changes, such as prescribing more calcium-rich foods and other treatments that may prevent the condition before it appears, rather than searching for ways to lessen its effects, said Lisa Bodnar, Ph.D., a maternal nutrition specialist at the University of Pittsburgh.
"There are no changes that a woman can make that will lessen symptoms or 'cure' her disease once she has overt preeclampsia. The dietary modifications that women should make are in early pregnancy, or even before a woman gets pregnant," Bodnar said.
Researchers and doctors originally prescribed diuretics to prevent preeclampsia because they thought the condition was caused by excess salt and water retained by pregnant women. Diuretics increase urination and remove water and salt from the body that can cause serious symptoms in liver, kidney and heart disease, including high blood pressure.
However, doctors stopped recommending diuretics as a regular preventive measure in the 1980s when studies began to link the pills with a decrease in pregnant women's plasma levels, the liquid part of blood that carries blood cells. Plasma levels normally increase as part of a healthy pregnancy.
Diuretics are still prescribed to pregnant women, although less than they used to be.
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The review was supported by Health Technology Assessment and the University of Liverpool in England.
Churchill D, et al. Diuretics for preventing pre-eclampsia (Review). Cochrane Database of Systematic Reviews 2007, Issue 1.
The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit cochrane/ for more information.
Contact: Lisa Esposito
Center for the Advancement of Health