Clinical Evidence Handbook

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Preeclampsia, Eclampsia, and Hypertension



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Am Fam Physician. 2009 May 15;79(10):895-896.

This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). See CME Quiz on page 857.

Preeclampsia (raised blood pressure and proteinuria) complicates 2 to 8 percent of pregnancies and increases morbidity and mortality in the mother and child.

  • Preeclampsia is more common in women with multiple pregnancies, and in persons with conditions associated with microvascular disease.

  • Calcium supplementation reduces the risk of preeclampsia compared with placebo.

Antiplatelet drugs (primarily low-dose aspirin) reduce the risk of preeclampsia, death of the baby, and premature birth, without increasing the risk of bleeding, in women at high risk of preeclampsia.
  • We do not know whether fish oil, evening primrose oil, salt restriction, magnesium supplementation, antioxidants, or glyceryl trinitrate is beneficial in women who are at high risk, because there are insufficient data to draw reliable conclusions.

  • We do not know whether atenolol reduces the risk of preeclampsia, but it may worsen outcomes for babies.

For women with mild to moderate hypertension during pregnancy, antihypertensive drugs reduce the risk of progression to severe hypertension, but may not improve other clinical outcomes.

  • Angiotensin-converting enzyme inhibitors have been associated with fetal renal failure, and beta blockers are associated with the baby being born small for its gestational age.

  • We do not know whether bed rest or hospital admission is also beneficial.

There is consensus that women who develop severe hypertension in pregnancy should receive antihypertensive treatment, but we do not know which antihypertensive agent is most effective.

  • We do not know whether plasma volume expansion, antioxidants, epidural analgesia, or early delivery improves outcomes for women with severe preeclampsia.

Magnesium sulphate reduces the risk of first or subsequent seizures in women with severe preeclampsia compared with placebo.

Magnesium sulphate reduces the risk of subsequent seizures in women with eclampsia compared with phenytoin or diazepam, with fewer adverse effects for the mother and baby.

Clinical Questions

What are the effects of preventive interventions in women at risk of preeclampsia?

Beneficial

Antiplatelet drugs

Calcium supplementation

Unknown effectiveness

Antioxidants

Glyceryl trinitrate

Magnesium supplementation

Marine oil (fish oil) and other prostaglandin precursors (evening primrose oil)

Salt restriction

Unlikely to be beneficial

Atenolol

What are the effects of interventions in women who develop mild to moderate hypertension during pregnancy?

Unknown effectiveness

Antihypertensive drugs for mild to moderate hypertension

Bed rest or admission versus outpatient care

What are the effects of interventions in women who develop severe preeclampsia or very high blood pressure during pregnancy?

Beneficial

Prophylactic magnesium sulphate in severe preeclampsia

Likely to be beneficial

Antihypertensive drugs for very high blood pressure*

Unknown effectiveness

Antioxidants in severe preeclampsia

Choice of analgesia during labor with severe preeclampsia

Early delivery for severe early-onset preeclampsia

Plasma volume expansion in severe preeclampsia

What is the best choice of anticonvulsant for women with eclampsia?

Beneficial

Magnesium sulphate (better and safer than other anticonvulsants)


*— There is consensus that women with severe hypertension during pregnancy should have antihypertensive treatment, and that women with eclampsia should have an anticonvulsant; placebo-controlled trials would therefore be unethical.

Clinical Questions

View Table

Clinical Questions

What are the effects of preventive interventions in women at risk of preeclampsia?

Beneficial

Antiplatelet drugs

Calcium supplementation

Unknown effectiveness

Antioxidants

Glyceryl trinitrate

Magnesium supplementation

Marine oil (fish oil) and other prostaglandin precursors (evening primrose oil)

Salt restriction

Unlikely to be beneficial

Atenolol

What are the effects of interventions in women who develop mild to moderate hypertension during pregnancy?

Unknown effectiveness

Antihypertensive drugs for mild to moderate hypertension

Bed rest or admission versus outpatient care

What are the effects of interventions in women who develop severe preeclampsia or very high blood pressure during pregnancy?

Beneficial

Prophylactic magnesium sulphate in severe preeclampsia

Likely to be beneficial

Antihypertensive drugs for very high blood pressure*

Unknown effectiveness

Antioxidants in severe preeclampsia

Choice of analgesia during labor with severe preeclampsia

Early delivery for severe early-onset preeclampsia

Plasma volume expansion in severe preeclampsia

What is the best choice of anticonvulsant for women with eclampsia?

Beneficial

Magnesium sulphate (better and safer than other anticonvulsants)


*— There is consensus that women with severe hypertension during pregnancy should have antihypertensive treatment, and that women with eclampsia should have an anticonvulsant; placebo-controlled trials would therefore be unethical.

Definition

Hypertension during pregnancy may be associated with one of several conditions. Pregnancy-induced hypertension is a rise in blood pressure, without proteinuria, during the second half of pregnancy. Preeclampsia is a multisystem disorder unique to pregnancy that is usually associated with raised blood pressure and proteinuria. It rarely presents before 20 weeks' gestation. Eclampsia is one or more convulsions in association with the syndrome of preeclampsia. Preexisting hypertension (not covered in this review) is known hypertension before pregnancy, or raised blood pressure before 20 weeks' gestation. It may be essential hypertension or, less commonly, secondary to underlying disease.

Incidence

Pregnancy-induced hypertension affects 10 percent of pregnancies, and preeclampsia complicates 2 to 8 percent of pregnancies. Eclampsia occurs in about one out of every 2,000 deliveries in resource-rich countries. In resource-poor countries, estimates of the incidence of eclampsia vary from one out of 100 to one out of 1,700.

Etiology

The cause of preeclampsia is unknown. It is likely to be multifactorial, and may result from deficient placental implantation during the first half of pregnancy. Preeclampsia is more common among women likely to have a large placenta, such as those with multiple pregnancies, and among women with medical conditions associated with microvascular disease, such as diabetes, hypertension, and collagen vascular disease. Other risk factors include genetic susceptibility, increased parity, and older maternal age. Cigarette smoking seems to be associated with a lower risk of preeclampsia, but this potential benefit is outweighed by an increase in adverse outcomes, such as low birthweight, placental abruption, and perinatal death.

Prognosis

The outcome of pregnancy in women with pregnancy-induced hypertension alone is at least as good as that for normotensive pregnancies. However, once preeclampsia develops, morbidity and mortality rise for both mother and child. For example, perinatal mortality for women with severe preeclampsia is double that for normotensive women. Perinatal outcome is worse with early gestational hypertension. Perinatal mortality also increases in women with severe essential hypertension.

Author disclosure: Lelia Duley is the author of studies included in this review.

search date: July 2007

Adapted with permission from Duley L. Pre-eclampsia, eclampsia, and hypertension. Clin Evid Handbook. December 2008:494–496. Please visit http://www.clinicalevidence.bmj.com for full text and references.

editor's note: In the United States, glyceryl trinitrate is usually called isosorbide mononitrate or dinitrate.

 

This is one in a series of chapters excerpted from the Clinical Evidence Handbook, published by the BMJ Publishing Group, London, U.K. The medical information contained herein is the most accurate available at the date of publication. More updated and comprehensive information on this topic may be available in future print editions of the Clinical Evidence Handbook, as well as online at http://www.clinicalevidence.bmj.com (subscription required). Those who receive a complimentary print copy of the Clinical Evidence Handbook from United Health Foundation can gain complimentary online access by registering on the Web site using the ISBN number of their book.



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