THIAZIDE VERSUS PLACEBO IN PROPHYLAXIS OF TOXEMIA OF PREGNANCY IN PRIMIGRAVID PATIENTS

Diuretics for preventing pre-eclampsia

BACKGROUND

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.

OBJECTIVES

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 (April 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2005, Issue 2) and EMBASE (2002 to April 2005).

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; relative risk (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; weighted 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).

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.

Overview of randomised trials of diuretics in pregnancy

Over the past 20 years at least 11 randomised trials of the prevention with diuretics of pre-eclampsia and its sequelae have been undertaken. Nine of these were reviewed. Reliable data from the remaining two were not available. The nine reviewed had investigated a total of nearly 7000 people. Significant evidence of prevention of "pre-eclampsia" was overwhelming, even when oedema was not included as a diagnostic criterion. But as the definitions of pre-eclampsia that had been used depended heavily on increases in blood pressure this evidence may simply have reflected the well known ability of diuretics to reduce blood pressure. When the data on perinatal death were reviewed a little difference was seen in postnatal survival. The incidence of stillbirths was reduced by about one third with treatment, but, perhaps owing to small numbers (only 37 stillbirths), the difference was not significant. Thus these randomised trials failed to provide reliable evidence of either the presence or the absence of any worthwhile effects of treatment with diuretics on perinatal mortality. The implications of this for current and future trials of beta blockers and other agents in the prevention of pre-eclampsia and its sequelae are that extremely large, ultra simple randomised trials are needed, of a size sufficient to permit direct assessment of the effects of treatment not on pre-eclampsia but on perinatal mortality itself. This may require the study of tens of thousands of pregnancies.

Diuretics in pregnancy: a case study of a worthless therapy

In the 1960s and 1970s diuretics were used during pregnancy to prevent and treat toxemia, but this therapy is now widely condemned as ineffective and harmful. The purpose of this paper was to study this example, to learn from it and to help to prevent further such examples. Data sources included selected articles in medical journals and text-books; in Finland drug catalogues, handbooks, unpublished sales data and interviews and questionnaires to physicians; in Sweden drug catalogues and sales data; controlled clinical trials were also analyzed. Analysis of the controlled clinical trials suggested that the whole episode of wide-spread diuretic use in pregnancy could have been avoided, if the available information had been used. A reason for the neglect of the critical information was apparently that the use of diuretics was in accordance with the common medical reasoning which values changes in clinical signs rather than looking for better health indicators. Use of diuretics was condemned in Finland later than, for example, in the United States, and decline in use occurred prior to the warnings in the local literature. Changes in practice seem to have occurred hierarchially and locally: opinions of a few leading obstetricians were crucial and they were rapidly and effectively disseminated to the providers of antenatal care in the domain of each obstetrician. This hierarchial dissemination of information has profound consequences for the attempts of understanding and influencing the prescribing habits of physicians.

Pharmacokinetics of furosemide in gestosis of pregnancy

Furosemid 50 mg was administered orally and intravenously to twelve gestotic women for brief periods as a part of a randomized, multicentre clinical trial comparing the efficacy of bed rest and pharmacological treatment. The pharmacokinetic profile was investigated using a gas-liquid chromatographic technique. The plasma half-life after oral and intravenous administration was 115 +/- 37.1 and 71.8 +/- 26.3 min and plasma clearance was 153 +/- 48 and 152 +/- 23 ml/min, respectively (mean +/- SD). Comparative data from healthy pregnant women cannot be obtained for ethical reasons. The results show that gestosis has only a marginal if any effect on the kinetics of furosemide in comparison with published kinetic parameters in healthy volunteers, and patients with renal failure. The new-born babies where checked for side effects according to a protocol in use in a larger regional surveillance programme. No clinical side-effects were attributable to furosemide, but the small size of the group does not permit any definitive conclusions about this aspect.

Hypertension and the obstetrician-gynecologist

Hypertension is a major risk factor for cardiovascular-related morbidity and death. Antihypertensive therapy markedly reduces the risk caused by elevated blood pressure. Earlier treatment of hypertensive patients should reduce deaths and morbidity even further. The obstetrician-gynecologist has the opportunity and responsibility to identify hypertensive patients early in the course of their disease. He must also confront the problem of elevated blood pressure associated with the use of oral contraceptives. In addition to its impact on the general population, chronic hypertension presents special problems during pregnancy. Pregnant women with elevated blood pressure have an increased fetal mortality rate and develop pre-eclampsia more frequently and earlier than nonhypertensive women. Antihypertensive treatment possibly increases fetal survival; when used appropriately, it definitely does not decrease fetal salvage. The appropriate use of antihypertensive therapy during pregnancy requires an understanding of the mechanism of action of these agents and recognition of side effects, especially those important during pregnancy.