The hypertensive disorders of pregnancy are major contributors to maternal and perinatal morbidity and mortality. In the mother, they can cause multiorgan system dysfunction including renal failure, hepatic failure, central nervous system (CNS) hemorrhage and stroke, pulmonary edema, placental abruption and disseminated intravascular coagulation (DIC). Fetal and neonatal complications include growth restriction, prematurity, and perinatal death.
Classification
The general classification of hypertensive disorders recommended by the Working Group Report on High Blood Pressure in Pregnancy and adopted by the American College of Obstetricians and Gynecologists (ACOG).
- Preeclampsia or eclampsia (hypertension and proteinuria unique to pregnancy)
- Chronic hypertension
- Chronic hypertension with superimposed preeclampsia
- Gestational or transient hypertension
The diagnosis of hypertension should be reserved for patients with a systolic blood pressure of greater than or equal to 140 mm Hg or a diastolic pressure of greater than or equal to 90 mm Hg. Blood pressure measurements should be taken in the sitting position after the woman has rested at least 10 minutes. Arterial pressures may also be taken in the lateral decubitus position, but the measurements should be corrected to the level of the right atrium.
PREECLAMPSIA/ECLAMPSIA
Preeclampsia is a syndrome unique to pregnancy, characterized by the new onset of hypertension and proteinuria in the latter half of gestation. Preeclampsia is classically considered to be a disease affecting the first pregnancy, but it also occurs in multiparas, especially if there are predisposing risk factors such as twins, diabetes mellitus, chronic hypertension, or a change in husband/partner. When it arises in the early second trimester (14 to 20 weeks), a hydatidiform mole or choriocarcinoma should be considered.
The following two criteria are essential for the diagnosis of preeclampsia:
- The development of hypertension (systolic blood pressure ≥ 140 mm Hg or diastolic blood pressure ≥ 90 mm Hg), in a woman whose blood pressures were previously normal, after the 20th week of pregnancy.
- The development of new-onset proteinuria after the 20th week of gestation. Proteinuria is defined as more than or equal to 0.3 g protein in a timed 24-hour urine collection.
Preeclampsia is divided into mild and severe forms, depending on the severity of hypertension, the amount of proteinuria, and the degree to which other organ systems are affected. Lists specific criteria for the diagnosis of severe preeclampsia
- Severe hypertension (systolic blood pressure ≥ 160 mm Hg, or diastolic blood pressure ≥ 110 mm Hg) at rest, on two occasions at least 6 hr apart.
- Heavy proteinuria (at least 5 g in a 24-hr collection or a qualitative value of 3+ in urine samples collected 4 hr apart).
- Oliguria (<500 mL in 24 hr)
- Cerebral or visual disturbances
- Pulmonary edema or cyanosis
- Epigastric or right upper quadrant pain
- Impaired liver function (elevated liver enzymes)
- Thrombocytopenia
- Fetal growth restriction
A variant of severe preeclampsia with particularly high morbidity is the HELLP syndrome. This syndrome occurs in preeclamptic women with evidence of hemolysis, elevated liver enzymes, and low platelets (thrombocytopenia). In contrast to more typical presentations of preeclampsia, the patient with HELLP syndrome is more likely to be multiparous, older than 25 years, and at less than 36 weeks’ gestation. Hypertension may be initially absent in 20% of the patients, whereas 30% will have mild elevations in blood pressure, and 50% will have severe elevations.
ECLAMPSIA
Eclampsia is the presence of tonic-clonic seizures in a woman with preeclampsia that cannot be attributed to other causes. Patients with severe preeclampsia are at the greatest risk for developing seizures, but the seizures can occur in so-called mild preeclamptic patients. Eclamptic seizures can also occur before the development of classic signs of preeclampsia. There is a wide range in the reported frequency and timing of eclamptic seizures. Clinical practices, including the use of magnesium sulfate intrapartum and postpartum for seizure prophylaxis in women with preeclampsia, as well as the timely recognition and delivery of women with severe preeclampsia, undoubtedly influence these numbers. In a recent review of this subject, 38% to 53% of eclamptic seizures occurred before labor, 18% to 36% occurred during labor, and 11% to 44% occurred after delivery (usually within the first 24 to 48 hours postpartum). When evaluating atypical cases of eclampsia (i.e., more than 48 hours postpartum or previous evidence of only mild disease) it is important to consider other causes of seizures such as underlying seizure disorder, hypertensive encephalopathy, metabolic abnormalities including hypoglycemia and hyponatremia, and CNS hemorrhage, thrombosis, mass, or infection.
CHRONIC HYPERTENSION
The diagnosis of chronic hypertension requires at least one of the following: known hypertension before pregnancy, development of hypertension before 20 weeks’ gestation, or, in cases in which hypertension is first noted during pregnancy, persistence of elevated blood pressures greater than 12 weeks’ postpartum.
Most pregnant women with chronic hypertension have essential hypertension, but a small percentage have secondary hypertension due to renal, vascular, endocrine, or behavioral causes (e.g., methamphetamine and cocaine use). Most of these conditions can be suspected on the basis of a thorough history and physical examination. Certain endocrine disorders, in particular hyperthyroidism, may present for the first time during pregnancy. Depending on the associated symptoms, signs, and response to medication, a workup to determine the etiology of the hypertension may be indicated. It is not uncommon for the physiologic stress of pregnancy to cause subclinical vascular or renal disease to become manifest. In these situations, it may be very difficult to differentiate between preeclampsia and an aggravated chronic hypertensive condition. Sometimes only careful follow-up postpartum will indicate the correct diagnosis.
CHRONIC HYPERTENSION WITH SUPERIMPOSED PREECLAMPSIA
Preeclampsia may become superimposed on chronic hypertensive disease. Superimposed preeclampsia can be very difficult to distinguish from poorly controlled chronic hypertension, especially if the woman is not seen until after the 20th week of gestation, but the two conditions are managed differently. In general, superimposed preeclampsia carries a worse prognosis than does either condition alone.
The diagnosis of superimposed preeclampsia should be reserved for those women with chronic hypertension who develop new-onset proteinuria (≥0.3 g in a 24-hour collection) after the 20th week of gestation. In pregnant women with preexisting hypertension and proteinuria, the diagnosis of superimposed preeclampsia should be considered if they experience sudden significant increases in blood pressure or proteinuria or any of the other signs and symptoms consistent with severe preeclampsia, including thrombocytopenia or abnormally elevated liver enzymes.