CTF Structured Abstract: Preeclampsia

Canadian Task Force on Preventive Health Care

Structured Abstract

Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Prevention of Preeclampsia*

Adapted by Marie-Dominique Beaulieu, MD, MSc, FCFP, Department of Family Medicine, University of Montreal from a report prepared for the US Preventive Services Task Force by Michelle Berlin, MD, MPH, and A. Eugene Washington, MD, MSc

These recommendations were finalized by the Task Force in January 1994

*Please note: Evidence from recently published studies has not yet been reviewed by the Task Force in terms of its potential effect on these recommendations.

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations for screening and treating pregnant women for preeclampsia in Canada.

Burden of Suffering

Although definitions differ, many define preeclampsia as acute hypertension presenting after the 20th week of gestation accompanied by abnormal edema and/or proteinuria (more than 0.3 g/24h), or both. BP over 140/90, or a rise of 15 mmHg or 30 mmHg above the usual diastolic and systolic BP respectively, is considered abnormal. Preeclampsia occurs in about 2.6% of all pregnancies. Women with preeclampsia are at increased risk for abruptio placenta, acute renal failure, cerebral hemorrhage, disseminated intravascular coagulation, pulmonary edema, circulatory collapse, and eclampsia. The fetus may become hypoxic, increasing risk of low birthweight, premature delivery, or perinatal death. Risk factors for preeclampsia and eclampsia include black ancestry, nulliparity or first pregnancy with the actual partner, multiple gestations, chronic hypertension or diabetes, a family history of eclampsia or preeclampsia and possibly obesity.

Options

Screening options include blood pressure monitoring throughout pregnancy, angiotensin II infusion test, supint pressor rollover examination, and evaluation of other clinical signs and symptoms such as edema, measurement of proteinuria, bacteriuria, and urine albumin. Prevention and treatment options include bed rest, prophylactic low-dose aspirin (60 to 150 mg/d), and early delivery of the child.

Outcomes

Sensitivity and specificity of the screening tests. Maternal and fetal death, pregnancy complications (abruptio placenta, acute renal failure, cerebral hemorrhage, disseminated intravascular coagulation, pulmonary edema, circulatory collapse, and eclampsia), birth complications (hypoxia, low birthweight, premature delivery) and development of chronic hypertension in the mother.

Evidence

These recommendations were adapted from a report prepared for the 1989 U.S. Preventive Services Task Force. MEDLINE was searched for 1966 - July 1993 using the keywords preeclampsia and prevention and control.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from December 1993 to January 1994. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

Screening is done to predict the development of preeclampsia (the diagnostic standard is based on clinical criteria). Renal lesions, a characteristic finding, are not present in 46% of women with preeclampsia. Measurable proteinuria occurs late in the course of the disease and therefore is not useful for screening. One prospective study of women between 24 and 34 weeks gestation showed urine albumin levels of 11 mcg/L had a sensitivity of 50% in predicting subsequent preeclampsia. The angiotensin infusion test is impractical and the supine rollover test has poor sensitivity and specificity.

Blood pressure measurement is the best indicator of preeclampsia-either absolute values or absence of the normal decline seen in the middle trimester of pregnancy. However, to be valid, the blood pressure must be measured in a consistent manner at each visit. A formula using the midtrimester values for mean arterial blood pressure has a sensitivity of 61% to 71% and a specificity of 62% to 74% in predicting preeclampsia.

RCTs with high-risk women have shown that low-dose aspirin reduces pregnancy-induced hypertension, preeclampsia, related uterine growth retardation, and cesarian section rates, but these decreases were not associated with a decrease in neonatal mortality. A large RCT of low-risk nulliparous women showed reduced rates of preeclampsia with aspirin use (6.3% to 4.6%) for women who had systolic blood pressure > 120 mm Hg. This reduction was associated with increased abruptio placenta, a finding not seen in another large RCT.

Bed rest, pharmacologic agents, and early delivery of the fetus decrease complications but have not been shown to improve outcomes. In general, studies dating back to the 1940s show that good prenatal care reduces preeclampsia but components of this care have not been evaluated.

Recommendations*

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

Fair evidence exists to recommend screening for preeclampsia in the PHE for all pregnant women. Blood pressure measurement should be done at all regular prenatal visits. [B, II-2, III]
Insufficient evidence exists to recommend for or against the use of low-dose aspirin in pregnant women with or without risk factors for preeclampsia [C, I].

Validation

This report was externally peer reviewed. The Canadian and American Colleges of Obstetricians and Gynecologists recommend blood pressure monitoring at the initial prenatal visit and every 4 weeks until 28 weeks' gestation, every 2 to 3 weeks until 36 weeks' gestation, and weekly thereafter. The 1989 U.S. Preventive Services Task Force recommended that all pregnant women should receive systolic and diastolic blood pressure monitoring throughout pregnancy.

Selected References

Source Document

Beaulieu M.D. Prevention of preeclampsia. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 136-43.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

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A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.