Diuretics for preventing pre-eclampsia

Not enough evidence for the use of diuretics for preventing pre-eclampsia.

Pre-eclampsia is a serious complication of pregnancy occurring in about 10% of women. It is identified by increased blood pressure and protein in the urine. Initially, women may not experience any symptoms. Constriction of blood vessels in the placenta, a feature of the disease, interferes with food and oxygen passing to the baby, thus slowing the baby's growth and sometimes it causes the baby to be born prematurely. Some women are affected by generalised swelling and, rarely, may have fits. Diuretic drugs cause people to excrete more urine and relax the blood vessels thus reducing the blood pressure. Because of these effects, it has been suggested that these drugs might prevent women from getting pre-eclampsia. On this basis, these drugs began to be used in pregnancy; however, it was thought that they might interfere with the normal expansion in the blood volume during pregnancy and thus increase the risk of pre-eclampsia. This review of five randomised controlled trials, involving 1836 women, sought to examine the evidence for diuretics for preventing pre-eclampsia. All trials compared diuretics with either placebo or no treatment. However, only four trials (1391 women) reported on pre-eclampsia. There were no significant differences in the outcomes except that diuretics were associated with more nausea and vomiting.

Authors' conclusions: 

There is insufficient evidence to draw reliable conclusions about the effects of diuretics on prevention of pre-eclampsia and its complications. However, from this review, no clear benefits have been found from the use of diuretics to prevent pre-eclampsia. Taken together with the level of adverse effects found, the use of diuretics for the prevention of pre-eclampsia and its complications cannot be recommended.

Read the full abstract...

Diuretics are used to reduce blood pressure and oedema in non-pregnant individuals. Formerly, they were used in pregnancy with the aim of preventing or delaying the development of pre-eclampsia. This practice became controversial when concerns were raised that diuretics may further reduce plasma volume in women with pre-eclampsia, thereby increasing the risk of adverse effects on the mother and baby, particularly fetal growth.


To assess the effects of diuretics on prevention of pre-eclampsia and its complications.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2010).

Selection criteria: 

Randomised trials evaluating the effects of diuretics for preventing pre-eclampsia and its complications.

Data collection and analysis: 

Three review authors independently selected trials for inclusion and extracted data. We analysed and double checked data for accuracy.

Main results: 

Five studies (1836 women) were included. All were of uncertain quality. The studies compared thiazide diuretics with either placebo or no intervention. There were no clear differences between the diuretic and control groups for any reported pregnancy outcomes including pre-eclampsia (four trials, 1391 women; risk ratio (RR) 0.68, 95% confidence interval (CI) 0.45 to 1.03), perinatal death (five trials,1836 women; RR 0.72, 95% CI 0.40 to 1.27), and preterm birth (two trials, 465 women; RR 0.67, 95% CI 0.32 to 1.41). There were no small-for-gestational-age babies in the one trial that reported this outcome, and there was insufficient evidence to demonstrate any clear differences between the two groups for birthweight (one trial, 20 women; mean difference 139 grams, 95% CI -484.40 to 762.40).

Thiazide diuretics were associated with an increased risk of nausea and vomiting (two trials, 1217 women; RR 5.81, 95% CI 1.04 to 32.46), and women allocated diuretics were more likely to stop treatment due to side effects compared to those allocated placebo (two trials, 1217 women; RR 1.85, 95% CI 0.81 to 4.22).