Pregnancy-induced hypertension

Preeclampsia and eclampsia are complications of pregnancy. In preeclampsia, the woman has dangerously high blood pressure, swelling, and protein in the urine. If allowed to progress, this syndrome will lead to eclampsia.

High blood pressure in pregnancy (hypertension) is a very serious complication. It puts both the mother and the fetus at risk for a number of problems. Hypertension can exist in several different forms. One of these is the preeclampsia-eclampsia continuum (also called pregnancy-induced hypertension or PIH). In this type of hypertension, high blood pressure is first noted sometime after week 20 of pregnancy and is accompanied by protein in the urine and swelling. Chronic hypertension is another form of hypertension. It usuallyexists before pregnancy or may develop before week 20 of pregnancy. Chronic hypertension with superimposed preeclampsia is another form of chronic hypertension. This syndrome occurs when a woman with pre-existing chronic hypertension begins to have protein in the urine after week 20 of pregnancy. Late hypertension is another form of high blood pressure. It usually occurs after week20 of pregnancy and is unaccompanied by protein in the urine and does not progress the way preeclampsia-eclampsia does.

Preeclampsia is most common among women who have never given birth. The disease is most common in mothers under the age of 20, or over the age of 35. African-American women have higher rates of preeclampsia than do Caucasian women.Other risk factors include poverty, multiple pregnancies (twins, triplets, etc.), pre-existing chronic hypertension, kidney disease, diabetes, excess amniotic fluid, and a condition of the fetus called nonimmune hydrops. The tendency to develop preeclampsia appears to run in families. The daughters and sisters of women who have had preeclampsia are more likely to develop the condition.

Experts are still trying to understand the exact causes of preeclampsia and eclampsia. It is generally accepted that preeclampsia and eclampsia are problematic because these conditions cause blood vessels to leak. The effects are seen throughout the body. When blood vessels leak they allow fluid to flow outinto the tissues of the body. The result is swelling in the hands, feet, legs, arms, and face. While many pregnant women experience swelling in their feet, and sometimes in their hands, swelling of the upper limbs and face is a sign of a more serious problem. As fluid is retained in these tissues, the woman may experience significant weight gain (two or more pounds per week).

Blood vessels also sometimes leak in the brain. They can cause severe damagewithin the brain, resulting in seizures or coma. If the blood vessels in theeyes begin to leak the woman may experience problems seeing, and may have blurry vision or may see spots. Also, the retina may become detached. When bloodvessels in the lungs leak fluid may leak into the tissues of the lungs, resulting in shortness of breath.

Leaky vessels within the liver may cause it to swell. The liver may be involved in a serious complication of preeclampsia, called the HELLP syndrome. In this syndrome, red blood cells are abnormally destroyed, chemicals called liver enzymes are abnormally high, and cells involved in the clotting of blood (platelets) are low. The small capillaries within the kidneys can leak. Normally, the filtration system within the kidney is too fine to allow protein (which is relatively large) to leave the bloodstream and enter the urine. In preeclampsia, however, the leaky capillaries allow protein to be dumped into the urine. The development of protein in the urine is very serious, and often results in a low birth weight baby.

In preeclampsia, the volume of circulating blood is lower than normal becausefluid is leaking into other parts of the body. The heart tries to make up for this by pumping a larger quantity of blood with each contraction. Blood vessels usually expand in diameter (dilate) in this situation to decrease the work load on the heart. In preeclampsia, however, the blood vessels are abnormally constricted, causing the heart to work even harder to pump against the small diameters of the vessels. This causes an increase in blood pressure.

The most serious consequences of preeclampsia and eclampsia include brain damage in the mother due to brain swelling and oxygen deprivation during seizures. Mothers can also suffer from blindness, kidney failure, liver rupture, andplacental abruption. Babies born to preeclamptic mothers are often smaller than normal, which makes them more susceptible to complications during labor,delivery, and in early infancy. Babies of preeclamptic mothers are also at risk of being born prematurely.

Diagnosing preeclampsia may be accomplished by noting painless swelling of the arms, legs, and/or face, in addition to abnormal weight gain. The patient'sblood pressure is taken during every doctor's visit during pregnancy. An increase of 30 mm Hg in the systolic pressure, or 15 mm Hg in the diastolic pressure, or a blood pressure reading greater than 140/90 mm Hg is considered indicative of preeclampsia. A simple laboratory test in the doctor's office canindicate the presence of protein in a urine sample (a dipstick test).

With mild preeclampsia, treatment may be limited to bed rest, with careful daily monitoring of weight, blood pressure, and urine protein via dipstick. This careful monitoring will be required throughout pregnancy, labor, delivery,and even for 2-4 days after the baby has been born. If the diastolic pressuredoes not rise over 100 mm Hg prior to delivery, and no other symptoms develop, the woman can continue pregnancy until the fetus is mature enough to be delivered safely. Ultrasound tests can be performed to monitor the health and development of the fetus.

If the diastolic blood pressure continues to rise over 100 mm Hg, or if othersymptoms like headache, vision problems, abdominal pain, or blood abnormalities develop, then the patient may require medications to prevent seizures. Magnesium sulfate is commonly given through a needle in a vein (intravenous, orIV). Medications that lower blood pressure (antihypertensive drugs) are reserved for patients with very high diastolic pressures (over 110 mm Hg), because lowering the blood pressure will decrease the amount of blood reaching thefetus. This places the fetus at risk for oxygen deprivation. If preeclampsiaappears to be progressing toward true eclampsia, then medications may be given in order to start labor. Babies can usually be delivered vaginally. After the baby is delivered, the woman's blood pressure and other vital signs will usually begin to return to normal quickly.

The prognosis in preeeclampsia and eclampsia depends on how carefully a patient is monitored. Very careful, consistent monitoring allows quick decisions to be made, and improves the woman's prognosis. Still, the most common causesof death in pregnant women are related to high blood pressure.

About 33% of all patients with preeclampsia will have the condition again with later pregnancies. Eclampsia occurs in about 1 out of every 200 women withpreeclampsia. If not treated, eclampsia is almost always fatal.

More information on how preeclampsia and eclampsia develop is needed before recommendations can be made on how to prevent these conditions. Research is being done with patients in high risk groups to see if calcium supplementation,aspirin, or fish oil supplementation may help prevent preeclampsia. Most importantly, it is clear that careful monitoring during pregnancy is necessary to diagnose preeclampsia early.

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