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

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

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.

  • 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.

What are the effects of preventive interventions in women at risk of preeclampsia?
BeneficialAntiplatelet drugs
Calcium supplementation
Unknown effectivenessAntioxidants
Glyceryl trinitrate
Magnesium supplementation
Marine oil (fish oil) and other prostaglandin precursors (evening primrose oil)
Salt restriction
Unlikely to be beneficialAtenolol
What are the effects of interventions in women who develop mild to moderate hypertension during pregnancy?
Unknown effectivenessAntihypertensive 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?
BeneficialProphylactic magnesium sulphate in severe preeclampsia
Likely to be beneficialAntihypertensive drugs for very high blood pressure*
Unknown effectivenessAntioxidants 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?
BeneficialMagnesium sulphate (better and safer than other anticonvulsants)


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.


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.


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.


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.

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