Hypertension in Pregnancy

Hypertension that develops during pregnancy is known as gestational hypertension. Gestational hypertension is defined as a systolic blood pressure equal to or greater than 140 mmHg and/or a diastolic blood pressure equal to or greater than 90 mmHg. Elevated blood pressure during pregnancy can be mild, moderate, or severe. Mild hypertension during pregnancy should be monitored but because of the vascular changes typical during pregnancy may not need to be treated with medication. (3, 4) Lifestyle changes including weight reduction, salt restriction, decreased alcohol consumption (no more than 1 drink per day), and smoking cessation lower blood pressure reducing the risk of complications during pregnancy. Eating a diet rich in potassium and calcium, fruits and vegetables (high fiber), and low fat dairy products, along with regular aerobic exercise contribute to successful weight loss. (1) Moderate to severe hypertension should be treated with medications and lifestyle changes. Reduction in activity level may become necessary. (1, 5) Recurrence of gestational hypertension is common especially in women who are overweight and who gain weight between pregnancies. Gestational hypertension is associated with the development of essential (chronic) hypertension. (6, 7)

Medications commonly used during pregnancy for hypertension include labetalol, hydralazine, or methyldopa. Metoprolol, a beta-blocker, may be added but caution should be used as beta-blockers may induce intrauterine growth retardation and at term induce beta blockade in the neonate. (8) Long-acting calcium channel blockers such as nifedipine can be added to methyldopa or labetalol if needed for severe hypertension. (9, 10) Thiazide diuretics, if needed, can be continued as long as volume depletion is avoided. ACE (angiotensin converting enzyme) inhibitors, ARBs (angiotensin II receptor blockers), and direct renin inhibitors are contraindicated after the first trimester of pregnancy as they cause fetal renal abnormalities. Nitroprusside is used only for uncontrollable hypertension and should be used less than four hours to prevent the risk of fetal cyanide poisoning. (1)

A condition called pre-eclampsia may complicate hypertensive pregnancies or may develop in initially normotensive women. In pre-eclampsia, patients either develop high blood pressure or their hypertension worsens accompanied by the spilling of protein in their urine after twenty weeks of gestation. The primary pathogenesis of pre-eclampsia begins with an abnormality of the placental vasculature resulting in decreased perfusion of the placenta that in turn leads to the release of factors that cause widespread maternal endothelial dysfunction. The endothelial dysfunction leads to multi-organ dysfunction. (11-15) Risk factors for pre-eclampsia are diabetes, obesity, decreased kidney function, and hypertension and a previous affected pregnancy.(1, 15, 16) Pre-eclampsia, when untreated, places the patient at risk for kidney injury, pulmonary edema, cerebral and liver hemorrhage, thrombocytopenia, seizures, abruptio placenta, and HELLP syndrome. The fetus is at risk for intrauterine growth retardation, premature birth, and stillbirth. (1, 15)

 

Symptoms of worsening pre-eclampsia include severe and/or persistent headache, visual changes, nausea, vomiting, shortness of breath, abdominal pain, decreased urine output, decreased fetal movement, vaginal bleeding, and preterm labor. If the patient experiences these symptoms, the patient should be instructed to seek immediate medical care. The cure for pre-eclampsia is delivery of the fetus. Depending on the gestational age of the fetus, delivery may need to be delayed. Prevention of the complications of pre-eclampsia should be instituted. These include starting magnesium sulfate to prevent maternal seizures, and, for pregnancies between 24 and 34 weeks of gestation, betamethasone to induce fetal lung maturation. (1, 2, 9, 15, 17-19) Treatment with antihypertensives does not change the course of the disease process but may be necessary if the patient’s hypertension becomes life threatening. Diuretics and reduction in activity level also do not alter the course of pre-eclampsia. (15)

In summary, hypertension during pregnancy should be monitored carefully during pregnancy. Life style modification and medications improve the pregnancy outcome in gestational hypertension. Gestational hypertension must be distinguished from pre-eclampsia as the etiology and treatment choices will differ. Pre-eclampsia should be monitored closely to prevent untoward complications for the mother and fetus.

References:

1. Report of the National High Blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy. Am J Obstet Gynecol. Jul 2000;183(1):S1-S22.
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18. Belfort MA, Anthony J, Saade GR, Allen JC, Jr. A comparison of magnesium sulfate and nimodipine for the prevention of eclampsia. N Engl J Med. Jan 23 2003;348(4):304-311.
19. Buchbinder A, Sibai BM, Caritis S, et al. Adverse perinatal outcomes are significantly higher in severe gestational hypertension than in mild preeclampsia. Am J Obstet Gynecol. Jan 2002;186(1):66-71.