Clinical:Hypertensive Disorders of Pregnancy

In obstetric clinical practice, hypertension is defined as a systolic blood pressure of at least 140 mmHg or a diastolic pressure of at least 90 mmHg during pregnancy and postpartum period. Hypertensive disorders in pregnancy are a spectrum of conditions complicating approximately 10% of all pregnancies worldwide. Approximately 30% of hypertensive disorders in pregnancy are due to chronic hypertension, and 70% of them is related to pregnancy. New-onset hypertension in pregnancy includes preeclampsia and gestational hypertension. Hypertensive disorders in pregnancy, and particularly preeclampsia, remain major causes of maternal and perinatal mortality, account for 15% of maternal deaths and 4% of perinatal deaths, and are a major risk factor for maternal and fetal morbidity (RR).

Classification

According to the last classification system by the National High Blood Pressure Education Working Group (2000), four main subtypes of hypertensive disorders in pregnancy were determined (Table 1) (RR).

Gestational hypertension

Diagnosis of gestational hypertension requires confirmation. The diagnosis of gestational hypertension is confirmed if preeclampsia has not developed and the blood pressure has returned to normal by 12 weeks postpartum. Gestational hypertension is a provisional diagnosis: 40% of women may go on to develop preeclampsia, while others may have preexisting chronic hypertension that has been masked by the physiological decrease in blood pressure that occurs during the first half of normal pregnancy (RR).

Preeclampsia

The exact incidence of preeclampsia is approximately 5-8% of all pregnancies depending of the population studied (RR). Preeclampsia is classified as mild (75%) or severe (25%) according to clinical findings (Table 2) (RR). It is essential to note that the distinction of mild and severe preeclampsia does not indicate different diseases. It can lead to multiple organ dysfunction syndrome, multi-system organ failure, or even death (RR). Eclampsia and HELLP syndrome are important complications of preeclampsia; in the presence of them, preeclampsia is considered as severe. Eclampsia and HELLP syndrome will be mentioned separately in the text.

Eclampsia

Eclampsia is defined as seizure activity with or without coma unrelated to epilepsy or other cerebral conditions in an obstetrical patient (RR). Approximately 2% of preeclamptic pregnancies develop eclampsia (RR). Although eclampsia is accepted as a severe form of preeclampsia, in clinical practice, it may occur in nearly one-third of patients without prior development of preeclampsia. In developed countries, eclampsia complicates about 1 in 2000 pregnancies; the onset of eclampsia can be antepartum/intrapartum (60%), or postpartum (40%) (RR). While most cases present in the third trimester of pregnancy or within the first 48 hours following delivery, rare cases have been reported prior to 20 weeks' gestation or beyond 48 hours (late postpartum) as late as 23 days postpartum (RR).

Hippocrates first described eclampsia when he wrote in one of his Aphorisms that "convulsions take place from either repletion or depletion" (RR). Hippocrates had observed the sudden and unexpected appearance of maternal grand-mal seizures, which occur when preeclampsia progresses to eclampsia, the word being derived from the Greek for "lightning". It was believed for many centuries that preeclampsia was a seizure disorder unique to pregnancy, but during the last 200 years this view of the disease has changed drastically and we now know that it is not only a convulsive disorder. Several new findings have led to this change in opinion. At the turn of the last century, the new ability to measure blood pressure led to demonstration of the association of preeclampsia and hypertension; hypertension was often found to precede the development of eclamptic seizures. These findings persuaded many to view the syndrome as a hypertensive rather than a seizure disorder (RR).

HELLP syndrome

The HELLP syndrome, originally described by Weinstein (RR) as an acronym in 1982, includes signs of hemolysis (H), elevated liver enzymes (EL), and low platelet count (LP), and is a variant presentation of severe preeclampsia. Approximately two-thirds of the cases of HELLP syndrome are first diagnosed antepartum with the remaining patients first recognized postpartum. The majority of the patients identified antepartum with HELLP syndrome are diagnosed between 27 and 37 weeks. Thus, antepartum HELLP syndrome is a complication of pregnancy that usually has fetal prematurity accompanying the onset of the disease process (RR).

The incidence of HELLP syndrome in women with severe preeclampsia and eclampsia ranges from 2% to 30% depending on the population studied and the criteria used to establish the diagnosis. HELLP syndrome commonly affects older women; this is a further distinction from the general association of preeclampsia with the young nulliparous female. This disorder occurs primarily in white, multiparous women above the age of 25 years, and is the most common cause of severe liver disease in pregnant women (RR).

HELLP syndrome is an atypical form of severe preeclampsia or eclampsia and a management dilemma for clinicians. Variable degrees of hepatic dysfunction, microangiopathic hemolytic anemia, and thrombocytopenia characterize this insidious disease process (27). As with severe preeclampsia, HELLP syndrome is associated with an increased risk of adverse outcomes, including placental abruption, renal failure, subcapsular hepatic hematoma, recurrent preeclampsia, preterm delivery, and even fetal or maternal death (RR).

Chronic hypertension

Chronic hypertension may be either essential (90%) or secondary to some identifiable underlying disorder, such as renal parenchymal or vascular disease, endocrine disorders, or coarctation of the aorta. About 30% of women with chronic hypertension develop preeclampsia during pregnancy. Women with chronic hypertension are also increased risk of preterm delivery, intrauterine fetal growth restriction or demise, placental abruption, congestive heart failure, and acute renal failure (RR).

Superimposed preeclampsia

Superimposed preeclampsia is diagnosed when a woman with chronic hypertension develops new-onset proteinuria after 20 weeks of pregnancy. The maternal and perinatal outcome is worse than with the de novo preeclampsia.

Table 1. Classification of the hypertensive disorders of pregnancy.

Table 2. Criteria of severe preeclampsia.