HYPERTENSION IN PREGNANCY

 

INTRODUCTION

There are four major causes of hypertension (high blood pressure) during pregnancy:

    ●Preeclampsia – Preeclampsia refers to the new onset of hypertension and evidence of organ injury in a pregnant woman during the latter half of gestation (after 20 weeks of pregnancy). Many organs can be affected, including the kidneys (leading to excess protein in the urine, called proteinuria), the liver, and the brain (leading to headaches and changes in vision and occasionally seizures). Preeclampsia can occur for the first time after delivery. The organ injury typically resolves within several days to weeks after delivery.

    ●Gestational hypertension (also called transient hypertension) – A diagnosis of gestational hypertension should be made in a woman who develops hypertension for the first time in pregnancy after 20 weeks of gestation and who has no other symptoms or signs of preeclampsia, such as protein in the urine (proteinuria). Over time, some women with gestational hypertension will develop proteinuria or other signs of preeclampsia and be considered to have preeclampsia, while others will be diagnosed with chronic hypertension because of persistently high blood pressure three months after delivery.

    ●Chronic hypertension – Chronic hypertension is defined as hypertension before pregnancy, whether or not the woman was on medication. Chronic hypertension should also be suspected in women who have hypertension before the 20^th week of pregnancy, although the diagnosis can only be confirmed once the pregnancy is over.

    ●Preeclampsia superimposed upon chronic hypertension – This term describes a woman with chronic hypertension who then develops preeclampsia after the 20^th week of pregnancy.

WHAT IS PREECLAMPSIA?

    Preeclampsia is a disorder that only occurs in pregnant and postpartum women. It is characterized by the new onset of hypertension and evidence of end-organ dysfunction (such as injury to the kidneys, liver, platelets, lungs, brain) diagnosed after 20 weeks of pregnancy. Hypertension is diagnosed when there is a persistent elevation in blood pressure of more than 140/90 mmHg. A single elevated blood pressure does not make the diagnosis of hypertension.

Preeclampsia is sometimes called by other names, including pregnancy-induced or pregnancy-associated hypertension and toxemia.

In the United States, preeclampsia occurs in 3 to 4 percent of pregnancies. Ninety percent of these cases occur after 34 weeks of gestation, and mostly at term (after 37 weeks of gestation).

WHO IS AT RISK FOR PREECLAMPSIA?

    Any pregnant woman can develop preeclampsia. However, some women are at higher risk than others. Women with one or more of the following characteristics are at increased risk for developing preeclampsia:

    ●First pregnancy (excluding miscarriages and abortions)

    ●Chronic hypertension, kidney disease, lupus, or diabetes prior to pregnancy

    ●A previous history of preeclampsia

    ●Gestational diabetes

    ●Multiple gestation (eg, twins or triplets)

    ●A family history of preeclampsia in a sister or mother

    ●Age under 20 years and possibly age over 35 to 40 years

    ●Obesity

WHAT CAUSES PREECLAMPSIA?

    Preeclampsia results from abnormalities in the development of the placenta very early in pregnancy. If the placenta does not invade deeply enough into the uterus and establish a healthy blood supply from the mother, it may not be able to supply itself or the fetus with adequate nutrients and oxygen as the pregnancy continues. This is especially problematic after 20 weeks of gestation when the fetus is growing rapidly. A cascade of events may occur that can damage blood vessels throughout the mother's body (in the kidneys, liver, brain) and cause the clinical syndrome that we call preeclampsia. Why this happens to some women and not others is not completely understood.

WHAT ARE THE SIGNS AND SYMPTOMS OF PREECLAMPSIA?

    Many women with preeclampsia have no symptoms of the disease. For this reason, prenatal visits to check for high blood pressure are scheduled frequently in the latter half of pregnancy.

Maternal — Most women with preeclampsia have mildly high blood pressure, a small amount of excess protein in the urine, and do not experience any symptoms of the disease. However, preeclampsia does not get better by itself during pregnancy and can worsen. This usually occurs over several days to weeks but may occur more quickly.

There are several signs and symptoms that, if present, place preeclampsia in the severe category. Only one of the signs/symptoms needs to be present for preeclampsia to be severe. The symptoms may be subtle, so patients should not hesitate to mention any concerns about possible symptoms of preeclampsia to their health care provider.

Symptoms that preeclampsia has progressed to the severe stage of the disease include:

    ●Persistent severe headache.

    ●Visual problems (blurred or double vision, blind spots, flashes of light or squiggly lines, loss of vision).

    ●New-onset shortness of breath (due to fluid in the lungs).

    ●Pain in the mid- or right-upper quadrant of the abdomen (similar to heartburn).

Signs that preeclampsia has progressed to the severe stage of the disease include:

    ●Blood pressure ≥160/110 mmHg on more than one occasion. Women with blood pressures in this range have an increased risk of stroke.

    ●Abnormal kidney tests (eg, serum creatinine >1.1 mg/dL).

    ●Low platelet count (<100,000/mL).

    ●Liver abnormalities (detected by blood tests).

    ●Pulmonary edema (fluid in the lungs).

    ●Seizure (one or more seizures in the setting of preeclampsia with no other conditions that could have caused the seizure is known as eclampsia).

Fetal — Preeclampsia can impair the ability of the placenta to provide adequate nutrition and oxygen to the fetus, which can have the following effects:

    ●Abnormal testing of fetal well-being (such as a nonreactive nonstress test or low biophysical profile score).

    ●Slowed growth of the fetus, usually noted by an ultrasound examination.

    ●Decreased amount of amniotic fluid around the fetus, usually noted by an ultrasound examination.

    ●Decreased blood flow through the umbilical cord, noted on Doppler tests (performed during ultrasound examination).

CAN PREECLAMPSIA BE PREVENTED?

    There are no tests that reliably predict who will get preeclampsia, and there is no way to completely prevent it. Doctors may recommend that women who have risk factors that place them at moderate or high risk for developing preeclampsia take low-dose aspirin to reduce this risk. Low-dose aspirin is usually started in the late first trimester (around 12 to 14 weeks) and continued into the third trimester of pregnancy (typically stopping at 36 weeks).

    Both the American College of Obstetricians and Gynecologists (ACOG) and the United States Preventive Services Task Force have published guidelines for selecting women at high risk for developing preeclampsia who may benefit from taking low-dose aspirin during pregnancy.Women at high risk include those with:

    ●Previous pregnancy with preeclampsia, especially early onset and with an adverse outcome

    ●Multifetal gestation

    ●Chronic hypertension

    ●Type 1 or 2 diabetes mellitus

    ●Renal disease

    ●Autoimmune disease (antiphospholipid syndrome, systemic lupus erythematosus)

    It is possible that women who have multiple less prominent risk factors for preeclampsia may also benefit from low-dose aspirin prevention, although this is not recommended in all cases. There are no known significant side effects from taking low-dose aspirin during pregnancy.

HOW IS PREECLAMPSIA TREATED?

    The only cure for preeclampsia is delivery of the fetus and placenta. Medication can lower blood pressure and thus reduce the risk of stroke in the mother, but these treatments do not improve the underlying abnormalities in the placenta and thus do not prevent progression of the disease.

    The management of pregnancies complicated by preeclampsia depends on the gestational age and whether severe features of the disease are present. The method of delivery (vaginal or cesarean birth) depends upon a number of factors, such as the position of the fetus, the dilation and effacement (thinning) of the cervix, and the fetus's condition. In most situations, vaginal delivery is possible.

Oxytocin  intravenously or Misoprostol in small dose is given to induce labor (stimulate the uterus to contract). If labor does not progress, or if complications develop that require the fetus to be delivered quickly, a cesarean birth may be indicated.

At term — Pregnancies complicated by preeclampsia at ≥37 weeks (ie, term) are delivered to initiate resolution of the disease and minimize the risk of harm to the woman or her fetus from worsening preeclampsia. Fetuses at or near term are not at high risk of complications from preterm birth and usually will not need to spend time in a special care nursery.

Before term — If preeclampsia develops before term and there are no severe features of the disease, it may be possible to delay delivery to 37 weeks to allow the fetus more time to grow and mature. However, if severe features of preeclampsia develop, delivery is often necessary to prevent complications in the woman or her fetus.

    While delivery is being delayed in women with preeclampsia without severe features before 37 weeks, the woman and fetus are closely monitored and steroids to reduce newborn risks from preterm delivery may be given:

    ●Maternal monitoring – When delivery is delayed, the mother and fetus will be monitored. Such women are typically admitted to the hospital. Maternal monitoring usually includes frequent blood pressure measurements and blood tests to check liver and kidney function, and platelet counts. Occasionally, such women may be allowed to stay at home, self-check their blood pressure, and have frequent office visits. Women who are monitored at home should call their health care provider immediately if any symptoms of severe disease develop.

    ●Fetal monitoring – Fetal monitoring includes a combination of nonstress tests and ultrasound examination.

    Nonstress testing is performed to monitor the fetus's condition. It is done by measuring the fetus's heart rate with a small device that is placed on the mother's abdomen. The device uses sound waves (ultrasound) to measure the fetus's heart rate over time, usually for 20 to 40 minutes. Normally, the fetus's baseline heart rate should be between 110 and 160 beats per minute. After 34 weeks, an increase in heart rate should occur periodically; the increase should be at least 15 beats per minute above the baseline heart rate for 15 seconds. The test is considered reassuring ("reactive") if two or more fetal heart rate increases (accelerations) are seen within a 20 minute period. Further testing may be needed if these increases are not observed after monitoring for 40 minutes. In general, outpatients undergo fetal testing twice per week, while inpatient testing is often performed daily.

    Ultrasound is used to monitor the fetus's growth, assess its well-being, and evaluate blood flow through the umbilical cord (called a Doppler test). A biophysical profile assesses well-being by using ultrasound to evaluate the fetus's movements, breathing activity, movement of the arms and legs, and amniotic fluid volume, and assigns a score to each of these variables. A high score is reassuring while a low score may indicate that the fetus would benefit from delivery. Ultrasound examinations to estimate the fetal weight are typically done every three to four weeks.

    ●Steroids – Fetuses delivered prematurely are at risk for breathing problems because their lungs may not be fully developed. Women who are likely to require preterm delivery (before 34 weeks of pregnancy) are usually given two steroid injections (eg, betamethasone) to speed fetal lung development. The steroids also decrease other potential complications of preterm birth, such as intraventricular hemorrhage (bleeding into the brain). The two injections are given 24 hours apart, and the full benefit of the treatment occurs 24 to 48 hours after the first injection.

WHAT HAPPENS DURING LABOR?

Because women with preeclampsia can develop eclampsia (seizures), most patients are treated with intravenous (IV) magnesium during labor and usually for 24 hours after delivery to prevent seizures. IV magnesium is safe for the fetus.

Severe hypertension is treated with one or more IV high blood pressure medications to reduce the risk of a maternal stroke.

WHAT HAPPENS AFTER DELIVERY?

High blood pressure and protein in the urine resolve after delivery, usually within a few days but sometimes it takes weeks. Mildly elevated blood pressure over a few weeks or months is not usually harmful. Severe hypertension should be treated, and some women will require a high blood pressure medication after being discharged from the hospital. This can be discontinued when the blood pressure returns to normal levels, usually within six weeks. Your provider may recommend monitoring blood pressure after discharge from the hospital either at his/her office or at home, and again in approximately 10 to 14 days to confirm resolution of the hypertension.

Blood pressure that continues to be elevated beyond 12 weeks after delivery is unlikely to be related to preeclampsia and may require long-term treatment. (See "Patient education: High blood pressure treatment in adults (Beyond the Basics)".)

Women who have preeclampsia appear to be at increased risk of cardiovascular disease later in life, including during the premenopausal period. They should discuss this risk with their health care provider. Lifestyle modifications (healthy diet, avoiding obesity and smoking) and management of lipid disorders, diabetes, and hypertension (if these disorders develop) can help to reduce the risk of cardiovascular problems.

WILL PREECLAMPSIA HAPPEN AGAIN IN FUTURE PREGNANCIES?

Women who develop preeclampsia are at increased risk of developing it in a subsequent pregnancy. Women with preeclampsia without severe features near term have only a 5 percent increased chance of developing it again. However, women who developed severe features of preeclampsia and were delivered before 30 weeks of gestation have a high risk (up to 70 percent) of preeclampsia in future pregnancies.

SUMMARY

    ●Women with preeclampsia develop high blood pressure (defined as a sustained elevation greater than 140/90 mmHg) and generally have protein in their urine, although some women develop other features of the disease without proteinuria. This can occur anytime during the last half of pregnancy (after 20 weeks of gestation) or in the first few days after delivery.

    ●Preeclampsia occurs in 3 to 4 percent of pregnancies in the United States. It is not known why some women develop preeclampsia while others do not. Currently, there are no tests that can reliably predict who will get the disease, and there is no way to completely prevent it. Taking low-dose aspirin in the late first trimester through the third trimester appears to lower the risk of developing preeclampsia in women at high risk of developing the disease.

    ●The majority of women with preeclampsia have no symptoms. The disease can progress quickly; symptoms of this may include headache, vision problems, shortness of breath, and upper abdominal pain.

    ●A pregnant woman should immediately call her health care provider if any of the signs or symptoms of severe disease develop, or if she has decreased fetal activity, vaginal bleeding, abdominal pain, or frequent uterine contractions.

    ●The only cure for preeclampsia is delivery of the fetus and placenta. Reduced physical activity, but not strict bed rest, and taking high blood pressure medication can lower the blood pressure but will not stop preeclampsia from worsening or reduce the risk of its complications.

    ●If tests monitoring the mother's or fetus's condition show concerning results, the health care provider may recommend delivery. A vaginal delivery is often possible.

    ●Because women with preeclampsia can develop seizures (called eclampsia), most women are treated with an anticonvulsant medication during labor and usually for 24 hours after delivery. Intravenous magnesium sulfate is the drug most commonly used to prevent seizures. It is safe for both mother and fetus.

    ●High blood pressure and protein in the urine resolve after delivery, usually within a few days or weeks. However, some women require medication to reduce high blood pressure after being discharged from the hospital.

    ●Most women who experience preeclampsia without severe features will not have it again in a future pregnancy. The risk of recurrence is higher in women with severe features of preeclampsia, especially when they occur in the second trimester.

    ●Women who develop preeclampsia appear to be at increased risk of developing cardiovascular disease later in life, so regular health care may be particularly important in this group of patients. Women who had high blood pressure during pregnancy should have their blood pressure checked yearly. They can also reduce their risk of having high blood pressure later in life by maintaining a healthy weight, limiting their salt intake, avoiding excess alcohol use, and exercising regularly.