Risks of Hypertension in Pregnancy

Important

If you have chronic hypertension, it is important to initiate prenatal care as soon as you know you are pregnant. Certain drugs for hypertension, notably ACE inhibitors, are associated with birth defects and should not be used during pregnancy. Your doctor will ensure that any medications you are using are safe during pregnancy and will closely monitor you throughout pregnancy for worsening hypertension, preeclampsia, and fetal growth restriction.

Women with chronic hypertension are at increased risk for preeclampsia and eclampsia, conditions that may endanger mother and baby. During your pregnancy, you are monitored for signs of preeclampsia, specifically proteinuria (protein in the urine), headaches, vision changes, and upper abdominal pain as part of regular prenatal care.

Pregnant women with chronic hypertension complicated by proteinuria are diagnosed with chronic hypertension and superimposed preeclampsia. Approximately 15 to 25% of women with chronic hypertension develop superimposed preeclampsia. Often, superimposed preeclampsia develops earlier in pregnancy than preeclampsia in women without preexisting hypertension. Superimposed preeclampsia also tends to be more severe and is often accompanied by fetal growth restriction. Treatment for both conditions is similar.

Chronic Hypertension

Chronic hypertension is a hypertensive disorder present before pregnancy. One of the most common medical complications of pregnancy, chronic hypertension may be diagnosed:

• if you have hypertension before becoming pregnant; or
• if your blood pressure before your 20th week of pregnancy is above 140 mmHg systolic or 90 mmHg diastolic on two occasions at least six hours apart.

Although chronic hypertension increases the risk for several conditions specific to pregnancy, most women with mild to moderate chronic hypertension do not experience complications. In fact, blood pressure control actually improves for the majority of pregnant women with underlying chronic hypertension.

In some cases, however, chronic hypertension worsens during pregnancy. Approximately 15 to 25% of women with chronic hypertension develop superimposed preeclampsia, which greatly increases the risk of complications for a mother and her baby (see below).

Superimposed Preeclampsia

Superimposed preeclampsia is a hypertensive disorder that usually develops after the 20th week of pregnancy and is characterized by chronic hypertension and proteinuria (protein in the urine). Edema (swelling) of the face and hands may also be present, but it is not required for the diagnosis. Table 1 summarizes the factors your doctor considers when diagnosing superimposed preeclampsia.

Symptoms of Superimposed Preeclampsia

Superimposed preeclampsia affects the functioning of many organs and causes various symptoms, ranging from mild to severe. Common symptoms associated with preeclampsia are listed in Table 2.

Women with mild preeclampsia are likely to experience only mildly elevated blood pressure and proteinuria. Distinguishing between mild and severe preeclampsia is important for identifying women who are at greater risk for developing eclampsia. However, at any time, mild preeclampsia can progress rapidly to severe, which is more likely to cause complications for mother and baby.

Whereas mild preeclampsia may not cause obvious symptoms, severe preeclampsia is marked by the abnormalities and symptoms listed in Table 2, including headache, abdominal pain, and visual disturbances. As the disorder progresses, so do proteinuria (protein in the urine), hypertension, and decreased platelet count. Women with severe preeclampsia are at increased risk of developing full-blown eclampsia (preeclampsia with seizure activity).

Complications of Superimposed Preeclampsia

Superimposed preeclampsia caused by chronic hypertension greatly increases the risk of complications for mother and baby, including:

• hypertensive encephalopathy (swelling of the cerebrum of the brain);
• heart failure;
• worsening of kidney problems;
• fetal growth restriction;
• fetal death
• placental abruption (separation of the placenta from the uterus);
• HELLP syndrome; and
• premature delivery.

Fetal growth restriction describes a condition in which blood flow to the placenta is decreased, depriving the fetus of nutrients and oxygen required for normal growth. Women with chronic hypertension are monitored closely throughout their pregnancies for signs of abnormal fetal growth.

Placental abruption (separation of the placenta from the uterus) causes bleeding between the uterus and the placenta and can lead to maternal anemia and kidney failure. In 50 to 85% of severe cases, this decrease in blood flow results in fetal death.

The HELLP syndrome is a variant of severe preeclampsia. It is characterized by:

• hemolysis (destruction of red blood cells);
• elevated liver enzymes (indicative of liver damage); and
• low blood platelet levels (indicative of impaired blood clotting, which may complicate labor, delivery, and beyond).

This condition complicates 10 to 20% of severe preeclampsia and eclampsia cases. It may develop before, during, or after delivery. Women with HELLP syndrome often complain of pain in the upper-right quadrant of the abdomen, nausea, vomiting, and malaise (a general ?unwell? feeling). Most women with HELLP syndrome have pre-existing high blood pressure and proteinuria.

If you have HELLP syndrome, both you and your baby are at high risk for complications. You may require transfusions of blood and blood products. If you develop kidney failure, you may require dialysis. There is a risk of bleeding in your liver or brain. Because these problems are so serious, your baby will be delivered within 48 hours of diagnosis (preferably vaginally, but through cesarean section if necessary). Therefore, your baby may be born prematurely. Otherwise, the treatment for HELLP syndrome is usually similar to that of severe preeclampsia.

This HealthMap guides you through the steps you and your doctor may take after you have been diagnosed with chronic hypertension and superimposed preeclampsia. Treatment varies according to the severity of the disorder, how close you are to term, whether you have any other health problems, and other possible factors. Learning about superimposed preeclampsia helps you actively participate in your treatment. When you see your doctor, raise any questions and concerns you may have. You may find it helpful to write questions down before you see your doctor or to take notes during your visits.