Preeclampsia is a disorder of widespread vascular endothelial
malfunction and vasospasm that occurs after 20 weeks' gestation and
can present as late as 4-6 weeks postpartum. It is clinically
defined by hypertension andproteinuria, with or without pathologic
edema.The incidence of preeclampsia in the United States is
estimated to range from 2% to 6% in healthy, nulliparous women.[1,
2, 3]Among all cases of the preeclampsia, 10% occur in pregnancies
of less than 34 weeks' gestation. The global incidence of
preeclampsia has been estimated at 5-14% of all pregnancies.In
developing nations, the incidence of the disease is reported to be
4-18%,[4, 5]with hypertensive disorders being the second most
common obstetric cause of stillbirths and early neonatal deaths in
these countries.[6]Medical consensus is lacking regarding the
values that define preeclampsia, but reasonable criteria in a woman
who was normotensive before 20 weeks' gestation include a systolic
blood pressure (SBP) greater than 140 mm Hg and a diastolic BP
(DBP) greater than 90 mm Hg on 2 successive measurements, 4-6 hours
apart. Preeclampsia in a patient with preexisting essential
hypertension is diagnosed if SBP has increased by 30 mm Hg or if
DBP has increased by 15 mm Hg.Mild and severe
preeclampsiaPreeclampsia is mild in 75% of cases and severe in 25%
of them.[7]In its extreme, the disease may lead to liver and renal
failure, disseminated intravascular coagulopathy (DIC), and central
nervous system (CNS) abnormalities. If preeclampsia-associated
seizures develop, the disorder has developed into the condition
calledeclampsia.Mild preeclampsia is defined as the presence of
hypertension (BP 140/90 mm Hg) on 2 occasions, at least 6 hours
apart, but without evidence of end-organ damage in the
patient.Severe preeclampsia is defined as the presence of 1 of the
following symptoms or signs in the presence of preeclampsia: SBP of
160 mm Hg or higher or DBP of 110 mm Hg or higher on 2 occasions at
least 6 hours apart Proteinuria of more than 5 g in a 24-hour
collection or more than 3+ on 2 random urine samples collected at
least 4 hours apart Pulmonary edema or cyanosis Oliguria (< 400
mL in 24 h) Persistent headaches Epigastric pain and/or impaired
liver function Thrombocytopenia Oligohydramnios, decreased fetal
growth, or placental abruptionClassification and Characteristics of
Hypertensive DisordersPreeclampsia is part of a spectrum of
hypertensive disorders that complicate pregnancy. As specified by
the National High Blood Pressure Education Program (NHBPEP) Working
Group, the classification is as follows[8]: Gestational
hypertension Chronic hypertension Preeclampsia/eclampsia
Superimposed preeclampsia (on chronic hypertension)Although each of
these disorders can appear in isolation, they are thought of as
progressive manifestations of a single process and are believed to
share a common etiology.Gestational hypertensionThe characteristics
of gestational hypertension are as follows: BP of 140/90 mm Hg or
greater for the first time during pregnancy No proteinuria BP
returns to normal less than 12 weeks' postpartum Final diagnosis
made only postpartumChronic hypertensionChronic hypertension is
characterized by either (1) a BP 140/90 mm Hg or greater before
pregnancy or diagnosed before 20 weeks' gestation; not attributable
to gestational trophoblastic disease or (2) hypertension first
diagnosed after 20 weeks' gestation and persistent after 12 weeks
postpartum.Preexisting chronic hypertension may present with
superimposed preeclampsia presenting as new-onset proteinuria after
20 weeks' gestation.Preeclampsia/eclampsiaPreeclampsia/eclampsia is
characterized by a BP of 140/90 mm Hg or greater after 20 weeks'
gestation in a women with previously normal BP and who have
proteinuria ( 0.3 g protein in 24-h urine specimen).Eclampsia is
defined as seizures that cannot be attributable to other causes, in
a woman with preeclampsiaSuperimposed preeclampsiaSuperimposed
preeclampsia (on chronic hypertension) is characterized by (1) new
onset proteinuria ( 300 mg/24 h) in a woman with hypertension but
no proteinuria before 20 weeks' gestation and (2) a sudden increase
in proteinuria or BP, or a platelet count of less than 100,000/mm3,
in a woman with hypertension and proteinuria before 20 weeks'
gestation.HELLP syndromeHELLP syndrome (hemolysis, elevated liver
enzyme, low platelets) may be an outcome of severe preeclampsia,
although some authors believe it to have an unrelated etiology. The
syndrome has been associated with particularly high maternal and
perinatal morbidity and mortality rates and may be present without
hypertension or, in some cases, without
proteinuria.ProteinuriaProteinuria is defined as the presence of at
least 300 mg of protein in a 24-hour urine collection. Some
investigators and clinicians have accepted a urine
protein-creatinine ratio of at least 0.3 as a criterion for
proteinuria, but the American College of Obstetricians and
Gynecologists (ACOG) has not yet incorporated this into their
definition.[9]In the emergency department, a urine
protein-to-creatinine ratio of 0.19 or greater is somewhat
predictive of significant proteinuria (negative predictive value
[NPV], 87%).[10]Serial confirmations 6 hours apart increase the
predictive value. Although more convenient, a urine dipstick value
of 1+ or more (30 mg/dL) is not reliable in the diagnosis of
proteinuria.PathophysiologyIn the fetus, preeclampsia can lead to
ischemic encephalopathy, growth retardation, and the various
sequelae of premature birth.Eclampsia is estimated to occur in 1 in
200 cases of preeclampsia when magnesium prophylaxis in not
administered. (See Seizure Prophylaxis.)[11, 12]Cardiovascular
diseaseAs previously mentioned, preeclampsia is characterized by
endothelial dysfunction in pregnant women. Therefore, the
possibility exists that preeclampsia may be a contributor to future
cardiovascular disease. In a meta-analysis, several associations
were observed between an increased risk of cardiovascular disease
and a pregnancy complicated by preeclampsia. These associations
included an approximately 4-fold increase in the risk of subsequent
development of hypertension and an approximately 2-fold increase in
the risk of ischemic heart disease, venous thromboembolism, and
stroke.[13]Moreover, women who had recurrent preeclampsia were more
likely to suffer from hypertension later in life.[13]In a review of
population-based studies, Harskamp and Zeeman noted a relationship
between preeclampsia and an increased risk of later chronic
hypertension and cardiovascular morbidity/mortality, compared with
normotensive pregnancy. Moreover, women who develop preeclampsia
before 36 weeks' gestation or who have multiple hypertensive
pregnancies were at highest risk.[14]Harskamp and Zeeman also found
that the underlying mechanism for the remote effects of
preeclampsia is complex and probably multifactorial. The risk
factors that are shared by cardiovascular disease and preeclampsia
are as follows: Endothelial dysfunction Obesity Hypertension
Hyperglycemia Insulin resistance Dyslipidemia
Metabolic syndrome, the investigators noted, may be a possible
underlying mechanism common to cardiovascular disease and
preeclampsia.Mechanisms behind preeclampsiaAlthough hypertension
may be the most common presenting symptom of preeclampsia, it
should not be viewed as the initial pathogenic process.The
mechanisms by which preeclampsia occurs is not certain, and
numerous maternal, paternal, and fetal factors have been implicated
in its development. The factors currently considered to be the most
important include the following[15]: Maternal immunologic
intolerance Abnormal placental implantation Genetic, nutritional,
and environmental factors Cardiovascular and inflammatory changes
Immunologic factors have long been considered to be key players in
preeclampsia. One important component is a poorly understood
dysregulation of maternal tolerance to paternally derived placental
and fetal antigens.[16]This maternal-fetal immune maladaptation is
characterized by defective cooperation between uterine natural
killer(NK) cells and fetal human leukocyte antigen (HLA)-C, and
results in histologic changes similar to those seen in acute graft
rejection. The endothelial cell dysfunction that is characteristic
of preeclampsia may be partially due to an extreme activation of
leukocytes in the maternal circulation, as evidenced by an
upregulation of type 1 helper T cells.Placentation in
PreeclampsiaPlacental implantation with abnormal trophoblastic
invasion of uterine vessels is a major cause of hypertension
associated with preeclampsia syndrome.[17, 18]In fact, studies have
shown that the degree of incomplete trophoblastic invasion of the
spiral arteries is directly correlated with the severity of
subsequent maternal hypertension. This is because the placental
hypoperfusion resulting from the incomplete invasion leads by an
unclear pathway to the release of systemic vasoactive compounds
that cause an exaggerated inflammatory response, vasoconstriction,
endothelial damage, capillary leak, hypercoagulability, and
platelet dysfunction, all of which contribute to organ dysfunction
and the various clinical features of the disease.Normal
placentation and pseudovascularizationIn normal pregnancies, a
subset of cytotrophoblasts called invasive cytotrophoblasts migrate
through the implantation site and invade decidua tunica media of
maternal spiral arteries and replace its endothelium in a process
called pseudovascularization.[19]The trophoblast differentiation
along the invasive pathway involves alteration in the expression of
a number of different classes of molecules, including cytokines,
adhesion molecules, extracellular matrix, metalloproteinases, and
the class Ib major histocompatibility complex (MHC) molecule,
HLA-G.[20, 21]For example, during normal differentiation, invading
trophoblasts alter their adhesion molecule expression from those
that are characteristic of epithelial cells (integrins alpha 6/beta
1, alpha V/beta 5, and E-cadherin) to those of endothelial cells
(integrins alpha 1/beta 1, alpha V/beta 3, and VE-cadherin).As a
result of these changes, the maternal spiral arteries undergo
transformation from small, muscular arterioles to large
capacitance, low-resistance vessels. This allows increased blood
flow to the maternal-fetal interface. Remodeling of these
arterioles probably begins in the first trimester and ends by 18-20
weeks' gestation. However, the exact gestational age at which the
invasion stops is unknown.Failure of pseudovascularization in
preeclampsiaThe shallow placentation noted in preeclampsia results
from the fact that the invasion of the decidual arterioles by
cytotrophoblasts is incomplete. This is due to a failure in the
alterations in molecular expression necessary for the
differentiation of the cytotrophoblasts, as required for
pseudovascularization. For example, the upregulation of matrix
metalloproteinase-9 (MMP-9) and HLA-G, 2 molecules noted in
normally invading cytotrophoblasts, does not occur.The invasive
cytotrophoblasts therefore fail to replace tunica media, which
means that mostly intact arterioles, which are capable of
vasoconstriction, remain. Histologic evaluation of the placental
bed demonstrates few cytotrophoblasts beyond the decidual layer.The
primary cause for the failure of these invasive cytotrophoblasts to
undergo pseudovascularization and invade maternal blood vessels is
not clear. However, immunologic and genetic factors have been
proposed. Early hypoxic insult to differentiating cytotrophoblasts
has also been proposed as a contributing factor.Endothelial
DysfunctionData show that an imbalance of proangiogenic and
antiangiogenic factors produced by the placenta may play a major
role in mediating endothelial dysfunction. Angiogenesis is critical
for successful placentation and the normal interaction between
trophoblasts and endothelium. (See Angiogenic Factors in
Preeclampsia, below.)Several circulating markers of endothelial
cell injury have been shown to be elevated in women who develop
preeclampsia before they became symptomatic. These include
endothelin, cellular fibronectin, and plasminogen activator
inhibitor-1, with an altered prostacyclin/thromboxane profile also
present.[22, 23]Evidence also suggests that oxidative stress,
circulatory maladaptation, inflammation, and humoral, mineral, and
metabolic abnormalities contribute to the endothelial dysfunction
and pathogenesis of preeclampsia.Angiogenic Factors in
PreeclampsiaThe circulating proangiogenic factors secreted by the
placenta include vascular endothelial growth factor (VEGF) and
placental growth factor (PlGF). The antiangiogenic factors include
soluble fms-like tyrosine kinase I receptor (sFlt-1) (otherwise
known as soluble VEGF receptor type I) and soluble endoglin
(sEng).VEGF and PlGFVEGF and PlGF promote angiogenesis by
interacting with the VEGF receptor family. Although both growth
factors are produced by placenta, the serum level of PlGF rises
much more significantly in pregnancy. In a study, Taylor et al
demonstrated that the serum level of PlGF decreased in women who
later developed preeclampsia.[24]The fall in serum level was
notable as early as the second trimester in women who developed
preeclampsia and intrauterine growth restriction.In another
investigation, Maynard et al observed that the serum levels of VEGF
and PlGF were decreased in women with preeclampsia.[25]However, the
magnitude of decrease was less pronounced for VEGF, as its serum
level was not as high as that of PlGF, even in normal pregnancy.
Other investigators have confirmed this finding and have shown that
the serum level of PlGF decreased in women before they developed
preeclampsia.[26, 27]Bills et al suggest that circulating VEGF-A
levels in preeclampsia are biologically active because of a loss of
repression of VEGF-receptor 1 signaling by PlGF-1, and VEGF165b may
be involved in the increased vascular permeability of
preeclampsia.[28]Soluble fms-like tyrosine kinase 1 receptorThe
receptor sFlt-1 is a soluble isoform of Flt-1, which is a
transmembrane receptor for VEGF. Although sFlt-1 lacks the
transmembrane domain, it contains the ligand-binding region and is
capable of binding circulating VEGF and PlGF, preventing these
growth factors from binding to transmembrane receptors. Thus,
sFlt-1 has an antiangiogenic effect.In addition to angiogenesis,
VEGF and PlGF are important in maintaining endothelial homeostasis.
Selective knockout of the glomerular VEGF gene has been shown to be
lethal in rats, whereas the heterozygotes were born with glomerular
endotheliosis (the renal lesion characteristic of preeclampsia) and
eventually renal failure. Furthermore, sFlt-1, when injected into
pregnant rats, produced hypertension and proteinuria along with
glomerular endotheliosis.[25]In addition to animal studies,
multiple studies in humans have demonstrated that excess production
of sFlt-1 is associated with an increased risk of preeclampsia. In
a case-control study that measured levels of sFlt-1, VEGF, and
PlGF, investigators found an earlier and greater increase in the
serum level of sFlt-1 in women who developed preeclampsia (21-24
wk) than in women who did not develop preeclampsia (33-36 wk),
whereas the serum levels of VEGF and PlGF deceased. Furthermore,
the serum level of sFlt-1 was higher in women who developed severe
preeclampsia or early preeclampsia (< 34 wk) than it was in
women who developed mild preeclampsia at term.[26]Soluble
endoglinsEng is a soluble isoform of co-receptor for transforming
growth factor beta (TGF-beta). Endoglin binds to TGF-beta in
association with the TGF-beta receptor. Because the soluble isoform
contains the TGF-beta binding domain, it can bind to circulating
TGF-beta and decrease circulating levels. In addition, TGF-beta is
a proangiogenic molecule, so the net effect of high levels of sEng
is anti-angiogenic.Several observations support the role of sEng in
the pathogenesis of preeclampsia. It is found in the blood of women
with preeclampsia up to 3 months before the clinical signs of the
condition, its level in maternal blood correlates with disease
severity, and the level of sEng in the blood drops after
delivery.[29]In studies on pregnant rats, administration of sEng
results in vascular permeability and causes hypertension. There is
also evidence that it has a synergistic relationship with sFlt-1,
because it increases the effects of sFlt-1 in pregnant rats; this
results in HELLP syndrome, as evidenced by hepatic necrosis,
hemolysis, and placental infarction.[30]Moreover, sEng inhibits
TGF-beta in endothelial cells and also inhibits TGF-beta-1
activation of nitric oxide mediated vasodilatation.Genetic Factors
in PreeclampsiaPreeclampsia has been shown to involve multiple
genes. Over 100 maternal and paternal genes have been studied for
their association with preeclampsia, including those known to play
a role in vascular diseases, BP regulation, diabetes, and
immunologic functions.Importantly, the risk of preeclampsia is
positively correlated between close relatives; a study showed that
20-40% of daughters and 11-37% of sisters of women with
preeclampsia also developed the disease.[16]Twin studies have shown
a high correlation as well, approaching 40%.Because preeclampsia is
a genetically and phenotypically complex disease, it is unlikely
that any single gene will be shown to play a dominant role in its
development.Additional Factors in PreeclampsiaOther substances that
have been proposed, but not proven, to contribute to preeclampsia
include tumor necrosis factor, interleukins, various lipid
molecules, and syncytial knots.[31]Risk Factors for PreeclampsiaThe
incidence of preeclampsia is higher in women with a history of
preeclampsia, multiple gestations, and chronic hypertension or
underlying renal disease. In addition, Lykke et al found that
preeclampsia, spontaneous preterm delivery, or fetal growth
deviation in a first singleton pregnancy predisposes women to those
complications in their second pregnancy, especially if the
complications were severe.[32]Gestational ageIn a registry-based
cohort study of 536,419 Danish women, delivery between 32 and 36
weeks gestation increased the risk of preterm delivery in the
second pregnancy from 2.7% to 14.7% and increased the risk of
preeclampsia from 1.1% to 1.8%. A first delivery before 28 weeks
increased the risk of a second preterm delivery to 26% and
increased the risk of preeclampsia to 3.2%.Preeclampsia in a first
pregnancy, with delivery between 32 and 36 weeks' gestation,
increased the risk of preeclampsia in a second pregnancy from 14.1%
to 25.3%. Fetal growth 2-3 standard deviations below the mean in a
first pregnancy increased the risk of preeclampsia from 1.1% to
1.8% in the second pregnancy.[32]Primigravid patients in particular
seem to be predisposed to preeclampsia.Maternal ageWomen aged 35
years and older have a markedly increased risk of
preeclampsia.RaceIn the United States, the incidence of
preeclampsia is 1.8% among white women and 3% in black
women.Additional risk factorsSome risk factors contribute to poor
placentation, whereas others contribute to increased placental mass
and poor placental perfusion secondary to vascular
abnormalities.[33]In addition to those discussed above,
preeclampsia risk factors also include the following: Hydatidiform
mole Obesity Thrombophilia Oocyte donation or donor insemination
Urinary tract infection Diabetes Collagen vascular disease
Periodontal disease[34]One literature review suggests that maternal
vitamin D deficiency may increase the risk of preeclampsia and
fetal growth restriction. Another study determined that vitamin D
deficiency/insufficiency was common in a group of women at high
risk for preeclampsia. However, it was not associated with the
subsequent risk of an adverse pregnancy outcome.[35]Studies have
suggested that smoking during pregnancy is associated with a
reduced risk of gestational hypertension and preeclampsia; however,
this is controversial.[21]Placenta previa has also been correlated
with a reduced risk of preeclampsia.Body weight is strongly
correlated with progressively increased preeclampsia risk, ranging
from 4.3% for women with a body mass index (BMI) < 20 kg/m2 to
13.3% in those with a BMI >35 kg/m2. A United Kingdom study on
obesity showed that 9% of extremely obese women were preeclamptic,
compared with 2% of matched controls.[36]Table 1 lists the risk
factors and their odds ratios for preeclampsia.[33]Table 1. Risk
Factors for Preeclampsia*(Open Table in a new
window)Nulliparity3:1
Age >40 y3:1
Black race1.5:1
Family history5:1
Chronic renal disease20:1
Chronic hypertension10:1
Antiphospholipid syndrome10:1
Diabetes mellitus2:1
Twin gestation (but unaffected by zygosity)4:1
High body mass index3:1
Angiotensinogen gene T235
Homozygous20:1
Heterozygous4:1
*Adapted from ACOG Technical Bulletin 219, Washington, DC
1996.[9]
Evaluation of PreeclampsiaBecause the clinical manifestations of
preeclampsia can be heterogeneous, diagnosing preeclampsia may not
be straightforward. In particular, because the final diagnosis of
gestational hypertension can only be made in retrospect, a
clinician may be forced to treat some women with gestational
hypertension as if they have preeclampsia. In addition, if a woman
has underlying renal or cardiovascular disease, the diagnosis of
preeclampsia may not become clear until the disease becomes
severe.Mild to moderate preeclampsia may be asymptomatic. Many
cases are detected through routine prenatal screening.Preeclampsia
in a previous pregnancy is strongly associated with recurrence in
subsequent pregnancies. A history of gestational hypertension or
preeclampsia should strongly raise clinical suspicion.Physical
findingsPatients with severe preeclampsia display end-organ effects
and may complain of the following: Headache Visual disturbances -
Blurred, scintillating scotomata Altered mental status Blindness -
May be cortical[22]or retinal Dyspnea Edema Epigastric or right
upper quadrant abdominal pain Weakness or malaise - May be evidence
of hemolytic anemiaEdema exists in many pregnant women, but a
sudden increase in edema or facial edema is suggestive of
preeclampsia. The edema of preeclampsia occurs by a distinct
mechanism that is similar to that of angioneurotic edema.Hepatic
involvement occurs in 10% of women with severe preeclampsia. The
resulting pain (epigastric or right upper quadrant abdominal pain)
is frequently accompanied by elevated serum hepatic transaminase
levels.The presence of clonus may indicate an increased risk of
convulsions.A study by Cooray et al found that the most common
symptoms that immediately precede eclamptic seizures are neurologic
symptoms (ie, headache, with or without visual disturbance),
regardless of degree of hypertension. This suggests that closely
monitoring patients with these symptoms may provide an early
warning for eclampsia.[37]Recurrence of preeclampsiaUncommonly,
patients have antepartum preeclampsia that is treated with delivery
but that recurs in the postpartum period.[38]Recurrent preeclampsia
should be considered in postpartum patients who present with
hypertension and proteinuria. (See Prognosis.)In patients who are
suffering a recurrence of preeclampsia, findings on physical
examination may include the following (see Prognosis): Altered
mental status Decreased vision or scotomas Papilledema Epigastric
or right upper quadrant abdominal tenderness Peripheral edema
Hyperreflexia or clonus: Although deep tendon reflexes are more
useful in assessing magnesium toxicity, the presence of clonus may
indicate an increased risk of convulsions. Seizures Focal
neurologic deficit
Measurement of HypertensionHypertension is diagnosed when 2 BP
readings of 140/90 mm Hg or greater are noted 6 hours apart within
a 1-week period. Measuring BP with an appropriate-sized cuff placed
on the right arm at the same level as the heart is important. The
patient must be sitting and, ideally, have had a chance to rest for
at least 10 minutes before the BP measurement. She should not be
lying down in a lateral decubitus position, as the arm often used
to measure the pressure in this position will be above the right
atrium.The Korotkoff V sound should be used for the diastolic
pressure. In cases in which the Korotkoff V sound is not present,
the Korotkoff IV sound may be used, but it should be noted as such.
The difference between the Korotkoff IV and V sounds may be as much
as 10 mm Hg. When an automated cuff is used, it must be able to
record the Korotkoff V sound. When serial readings are obtained
during an observational period, the higher values should be used to
make the diagnosis.Lack of hypertension on examinationAlthough
hypertension is an important characteristic of preeclampsia,
because the underlying pathophysiology of preeclampsia is a diffuse
endothelial cell disorder influencing multiple organs, hypertension
does not necessarily need to precede other preeclamptic symptoms or
laboratory abnormalities. Presenting symptoms other than
hypertension may include, as previously mentioned, edema, visual
disturbances, headache, and epigastric or right upper quadrant
tenderness.Diagnostic ConsiderationsGestational hypertensionDuring
diagnosis, preeclampsia must be differentiated from gestational
hypertension; although gestational hypertension is more common and
may present with symptoms similar to those of preeclampsia,
including epigastric discomfort or thrombocytopenia, it is which is
not characterized by proteinuria. (See Classification and
Characteristics of Hypertensive Disorders.)Placental
hypoperfusionPlacental hypoperfusion or ischemia in preeclampsia
has many causes. Preexisting vascular disorders, such as
hypertension and connective tissue disorders, can result in poor
placental circulation. In cases of multiple gestation or increased
placental mass, it is not surprising for the placenta to become
underperfused. However, most women who develop preeclampsia are
healthy and do not have underlying medical conditions. In this
group of women, abnormally shallow placentation has been shown to
be responsible for placental hypoperfusion. (See Placentation in
Preeclampsia.)Differential diagnosisAbdominal Trauma, BluntAbruptio
PlacentaeAneurysm, AbdominalAppendicitis, AcuteCholecystitis and
Biliary ColicCholelithiasisCongestive Heart Failure and Pulmonary
EdemaDomestic ViolenceEarly Pregnancy LossEncephalitisHeadache,
TensionHypertensive EmergenciesHyperthyroidism, Thyroid Storm, and
Graves DiseaseMigraine HeadacheOvarian TorsionPregnancy,
EclampsiaStatus EpilepticusStroke, HemorrhagicStroke,
IschemicSubarachnoid HemorrhageSubdural HematomaThrombotic
Thrombocytopenic PurpuraToxicity, AmphetamineToxicity,
SympathomimeticToxicity, Thyroid HormoneTransient Ischemic
AttackUrinary Tract Infection, FemaleWithdrawal
SyndromesCerebrovascular accidentsSeizure disordersBrain
tumorsMetabolic diseasesMetastaticgestational trophoblastic
diseaseThrombotic thrombocytopenic purpuraRoutine StudiesAll women
who present with new-onset hypertension should have the following
laboratory tests: Complete blood cell (CBC) count Serum alanine
aminotransferase (ALT) and aspartate aminotransferase (AST) levels
Serum creatinine Uric acidIn addition, a peripheral smear should be
performed, serum lactate dehydrogenase (LDH) levels should be
measured, and an indirect bilirubin should be carried out if HELLP
syndrome is suspected. Although a coagulation profile (prothrombin
time [PT], activated partial [aPTT], and fibrinogen) should also be
evaluated, the clinical use of routine evaluation is unclear when
the platelet count is 100,000/mm3 or more with no evidence of
bleeding.[39]Laboratory values for preeclampsia and HELLP syndrome
[8, 40]Renal values are as follows: Proteinuria of >300 mg/24 h
Urine dipstick >1+ Protein/creatinine ratio >0.3* Serum uric
acid >5.6 mg/dL* Serum creatinine >1.2
mg/dLPlatelet/coagulopathy-related results are as follows: Platelet
count < 100,000/mm3 Elevated PT or aPTT* Decreased fibrinogen*
Increased d-dimer*Hemolysis-related results are as follows:
Abnormal peripheral smear* Indirect bilirubin >1.2 mg/dL*
Lactate dehydrogenase >600 U/L*In addition, elevated liver
enzymes (serum AST >70 U/L) are found in preeclampsia and HELLP
syndrome.[19]Urine testsTo diagnose proteinuria, a 24-hour urine
collection for protein and creatinine should be obtained whenever
possible. Up to 30% of women with gestational hypertension who have
trace protein noted on random urine samples may have 300 mg of
protein in a 24-hour urine collection.[41]Thus, a 24-hour urine
protein analysis remains the criterion standard for proteinuria
diagnosis. Alternatively, greater than 1+ protein on a dipstick
analysis on a random sample is sufficient to make the diagnosis of
proteinuria.Random urine samples can be used to calculate the
protein-creatinine ratio. Thresholds of 0.14-0.3 have been proposed
for diagnosing proteinuria.[42]However, there is no agreement yet
as to the best threshold for identifying pregnant women with
significant proteinuria. Moreover, up to 10% of patients with
preeclampsia and 20% of patients with eclampsia may not have
proteinuria.[43, 44](HELLP syndrome has been known to occur without
hypertension or proteinuria.)Hyperuricemia is one of the earliest
laboratory manifestations of preeclampsia. It has a low
sensitivity, ranging from 0% to 55%, but a relatively high
specificity of 77-95%.[45]Serial levels may be useful to indicate
disease progression.Baweja et al suggest that when measuring
urinary albumin using high-performance liquid chromatography in an
early and uncomplicated pregnancy, spot urinary albumin:creatinine
ratio (ACR) values are higher. If measured early in the second
trimester, an ACR of 35.5 mg/mmol or higher may predict
preeclampsia before symptoms arise.[46]Congo red dyeA study at Yale
University has shown preliminary results that Congo red, a dye
currently used to locate atypical amyloid aggregates in Alzheimer
disease, may also be effective in the early diagnosis of
preeclampsia.[45]This finding may lead to a spot urine test that
can be used in emergency departments and internationally,
especially in resource-poor countries where preeclampsia continues
to be underdiagnosed and accounts for a large percentage of
maternal and fetal mortality.Liver enzymesAlthough controversy
exists over the threshold for elevated liver enzyme, the values
proposed by Sibai et al (AST of >70 U/L and LDH of >600 U/L)
appear to be the most widely accepted. Alternatively, values that
are 3 standard deviations away from the mean for each laboratory
value may be used for AST.[40]HistologyThe presence of
schistocytes, burr cells, or echinocytes on peripheral smears, or
elevated indirect bilirubin and low serum heptoglobin levels, may
be used as evidence of hemolysis in diagnosing HELLP syndrome. The
differential diagnosis for HELLP syndrome must include various
causes for thrombocytopenia and liver failure such as acute fatty
liver of pregnancy,hemolytic uremic syndrome,acute pancreatitis,
fulminant hepatitis,systemic lupus erythematosus,cholecystitis, and
thrombotic thrombocytopenic purpura.Additional laboratory
testsOther laboratory values suggestive of preeclampsia include an
elevation in hematocrit and a rise in serum creatinine and/or uric
acid. Although these laboratory abnormalities increase the
suspicion for preeclampsia, none of these laboratory tests should
be used to diagnose preeclampsia.CT Scanning and MRIComputed
tomography (CT) scanning and magnetic resonance imaging (MRI) scans
have revealed numerous abnormalities in patients with eclampsia,
such as cerebral edema, focal infarction, intracranial hemorrhage,
and posterior leukoencephalopathy.[47]Currently, however, there is
no pathognomonic CT scan or MRI finding for eclampsia. Furthermore,
cerebral imaging is not necessary for the conditions diagnosis and
management. However, head CT scanning is used to detect
intracranial hemorrhage in selected patients with sudden severe
headaches, focal neurologic deficits, seizures with a prolonged
postictal state, or atypical presentation for
eclampsia.UltrasonographyUltrasonography is used to assess the
status of the fetus as well as to evaluate for growth restriction
(typically asymmetricaluse abdominal circumference). Aside from
transabdominal ultrasonography, umbilical artery Doppler
ultrasonography should be performed to assess blood flow. The value
of Doppler ultrasonography in other fetal vessels has not been
demonstrated.CardiotocographyCardiotocography is the standard fetal
nonstress test and the mainstay of fetal monitoring. Although it
gives continuing information about fetal well being, it has little
predictive value.Management of PreeclampsiaThe optimal management
of a woman with preeclampsia depends on gestational age and disease
severity. Because delivery is the only cure for preeclampsia,
clinicians must try to minimize maternal risk while maximizing
fetal maturity. The primary objective is the safety of the mother
and then the delivery of a healthy newborn. Obstetric consultation
should be sought early to coordinate transfer to an obstetric
floor, as appropriate.[48]Patients with mild preeclampsia are often
induced after 37 weeks' gestation. Before this, the immature fetus
is treated with expectant management with corticosteroids to
accelerate lung maturity in preparation for early delivery.In
patients with severe preeclampsia, induction of delivery should be
considered after 34 weeks' gestation. In these cases, the severity
of disease must be weighed against the risks of infant prematurity.
In the emergency setting, control of BP and seizures should be
priorities. In general, the further the pregnancy is from term, the
greater the impetus to manage the patient medically.Prehospital
TreatmentPrehospital care for pregnant patients with suspected
preeclampsia includes the following: Oxygen via face mask
Intravenous access Cardiac monitoring Transportation of patient in
left lateral decubitus position Seizure precautionsCare in Mild
PreeclampsiaBefore 37 weeks, expectant management is appropriate.
In most cases, patients should be hospitalized and monitored
carefully for the development of worsening preeclampsia or
complications of preeclampsia. Although randomized trials in women
with gestational hypertension and mild preeclampsia demonstrate the
safety of outpatient management with frequent maternal and fetal
evaluations, most of the patients in these studies had mild
gestational hypertension.[49]Therefore, the safety of managing a
woman with mild preeclampsia as an outpatient still needs to be
investigated.Although bedrest has been recommended in women with
preeclampsia, little evidence supports its benefit. In fact,
prolonged bed rest during pregnancy increases the risk of
thromboembolism.A pregnancy complicated by mild preeclampsia at or
beyond 37 weeks should be delivered. Although the pregnancy outcome
is similar in these women as it is in women with a normotensive
pregnancy, the risk of placental abruption and progression to
severe disease is slightly increased.[50, 51]Thus, regardless of
cervical status, induction of labor should be recommended. Cesarean
section may be performed based on standard obstetric
criteria.Antepartum testing is generally indicated during expectant
management of patients with mild preeclampsia. However, there is
little consensus regarding the types of tests to be used and the
frequency of testing. Most clinicians offer a nonstress test (NST)
and a biophysical profile (BPP) at the time of the diagnosis and
usually twice per week until delivery.[33, 9]If a patient is at 34
weeks' gestation or more and has ruptured membranes, abnormal fetal
testing, progressive labor, or fetal growth restriction in the
setting of mild preeclampsia, delivery is recommended.Care in
Severe PreeclampsiaWhen severe preeclampsia is diagnosed after 34
weeks' gestation, delivery is most appropriate. The mode of
delivery should depend on the severity of the disease and the
likelihood of a successful induction. Whenever possible, however,
vaginal delivery should be attempted and cesarean section should be
reserved for routine obstetric indications.Women with severe
preeclampsia who have nonreassuring fetal status, ruptured
membranes, labor, or maternal distress should be delivered
regardless of gestational age. If a woman with severe preeclampsia
is at 32 weeks' gestation or more and has received a course of
steroid, she should be delivered as well.Patients presenting with
severe, unremitting headache, visual disturbance, and right upper
quadrant tenderness in the presence of hypertension and/or
proteinuria should be treated with utmost caution.Expectant
management of severe preeclampsiaIf a patient presents with severe
preeclampsia before 34 weeks' gestation but appears to be stable,
and if the fetal condition is reassuring, expectant management may
be considered, provided that the patient meets the strict criteria
set by Sibai et al (see Laboratory values for preeclampsia and
HELLP syndrome).[52]This type of management should be considered
only in a tertiary center. In addition, because delivery is always
appropriate for the mother, some authorities consider delivery as
the definitive treatment regardless of gestational age. However,
delivery may not be optimal for a fetus that is extremely
premature. Therefore, in a carefully chosen population, expectant
management may benefit the fetus without greatly compromising
maternal health.All of these patients must be evaluated in a labor
and delivery unit for 24 hours before a decision for expectant
management can be made. During this period, maternal and fetal
evaluation must show that the fetus does not have severe growth
restriction or fetal distress. In addition, maternal urine output
must be adequate. The woman must have essentially normal laboratory
values (with the exclusive exception of mildly elevated liver
function test results that are less than twice the normal value)
and hypertension that can be controlled.Fetal monitoring should
include daily nonstress testing and ultrasonography performed to
monitor for the development of oligohydramnios and decreased fetal
movement. In addition, fetal growth determination at 2-week
intervals must be performed to document adequate fetal growth. A
24-hour urine collection for protein may be repeated.
Corticosteroids for fetal lung maturity should be administered
prior to 34 weeks.Daily blood tests should be performed for liver
function tests (LFTs), CBC count, uric acid, and LDH. Patients
should be instructed to report any headache, visual changes,
epigastric pain, or decreased fetal movement.Criteria for
deliveryWomen with severe preeclampsia who are managed expectantly
must be delivered under the following circumstances: Nonreassuring
fetal heart status Uncontrollable BP Oligohydramnios, with amniotic
fluid index (AFI) of less than 5 cm Severe intrauterine growth
restriction in which the estimated fetal weight is less than 5%
Oliguria (< 500 mL/24 h) Serum creatinine level of at least 1.5
mg/dL Pulmonary edema Shortness of breath or chest pain with pulse
oximetry of < 94% on room air Headache that is persistent and
severe Right upper quadrant tenderness Development of HELLP
syndromeSeizure Treatment and Prophylaxis With Magnesium SulfateThe
basic principles of airway, breathing, and circulation (ABC) should
always be followed as a general principle of seizure
management.Magnesium sulfate is the first-line treatment for the
prevention of primary and recurrent eclamptic seizures. For
eclamptic seizures that are refractory to magnesium sulfate,
lorazepam and phenytoin may be used as second-line agents.Active
seizures should be treated with intravenous magnesium sulfate as a
first-line agent.[7]A loading dose of 4 g should be given by an
infusion pump over 5-10 minutes, followed by an infusion of 1 g/h
maintained for 24 hours after the last seizure. Recurrent seizures
should be treated with an additional bolus of 2 g or an increase in
the infusion rate to 1.5 g or 2 g per hour.Prophylactic treatment
with magnesium sulfate is indicated for all patients with severe
preeclampsia. However, no consensus exists as to whether patients
with mild preeclampsia need magnesium seizure prophylaxis. Although
ACOG recommends magnesium sulfate in severe preeclampsia, it has
not recommended this therapy in all cases of mild preeclampsia.Some
practitioners withhold magnesium sulfate if BP is stable and/or
mildly elevated and if the laboratory values for LFTs and platelets
are mildly abnormal and/or stable. Other physicians feel that even
patients with gestational hypertension should receive magnesium, as
a small percentage of these patients may either have preeclampsia
or may develop it. The ultimate decision should depend on the
comfort level of the labor and delivery staff in administering
intravenous (IV) magnesium sulfate. An estimated 100 patients need
to be treated with magnesium sulfate therapy to prevent 1 case of
eclampsia.[53, 7, 54]Acute Treatment of Severe Hypertension in
PregnancyIn the setting of severe hypertension (SBP >160 mm Hg;
DBP >110 mm Hg), antihypertensive treatment is recommended. The
goal of hypertension treatment is to lower BP to prevent
cerebrovascular and cardiac complications while maintaining
uteroplacental blood flow (ie, maintain BP around 140/90 mm Hg).
However, although antihypertensive treatment decreases the
incidence of cerebrovascular problems, it does not alter the
progression of preeclampsia. Control of mildly increased BP does
not appear to improve perinatal morbidity or mortality, and it may,
in fact, reduce birth weight.HydralazineHydralazine is a direct
peripheral arteriolar vasodilator and, in the past, was widely used
as the first-line treatment for acute hypertension in
pregnancy.[55, 56]This agent has a slow onset of action (10-20 min)
and peaks approximately 20 minutes after administration.
Hydralazine should be given as an IV bolus at a dose of 5-10 mg,
depending on the severity of hypertension, and may be administered
every 20 minutes up to a maximum dose of 30 mg.The side effects of
hydralazine are headache, nausea, and vomiting. Importantly,
hydralazine may result in maternal hypotension, which can
subsequently result in a nonreassuring fetal heart rate tracing in
the fetus.[8]In a meta-analysis, Magee et al pointed out that
hydralazine was associated with worse maternal and perinatal
outcomes than were labetalol and nifedipine. Furthermore,
hydralazine was associated with more maternal side effects than
were labetalol and nifedipine.[55]LabetalolLabetalol is a selective
alpha blocker and a nonselective beta blocker that produces
vasodilatation and results in a decrease in systemic vascular
resistance. The dosage for labetalol is 20 mg IV with repeat doses
(40, 80, 80, and 80 mg) every 10 minutes up to a maximum dose of
300 mg. Decreases in BP are observed after 5 minutes (in contrast
to the slower onset of action of hydralazine), and the drug results
in less overshoot hypertension than does hydralazine.Labetalol
decreases supraventricular rhythm and slows the heart rate,
reducing myocardial oxygen consumption. No change in afterload is
observed after treatment with labetalol. The side effects of
labetalol are dizziness, nausea, and headaches. After satisfactory
control with IV administration has been achieved, an oral
maintenance dose can be started.[8, 55]NifedipineCalcium channel
blockers act on arteriolar smooth muscle and induce vasodilatation
by blocking calcium entry into the cells. Nifedipine is the oral
calcium channel blocker that is used in the management of
hypertension in pregnancy. The dosage of nifedipine is 10 mg PO
every 15-30 minutes, with a maximum of 3 doses. The side effects of
calcium channel blockers include tachycardia, palpitations, and
headaches. Concomitant use of calcium channel blockers and
magnesium sulfate is to be avoided. Nifedipine is commonly used
postpartum in patients with preeclampsia, for BP control.[8,
55]Sodium nitroprussideIn a severe hypertensive emergency, when the
above-mentioned medications have failed to lower BP, sodium
nitroprusside may be given. Nitroprusside results in the release of
nitric oxide, which in turn causes significant vasodilation.
Preload and afterload are then greatly decreased. The onset of
action is rapid, and severe rebound hypertension may result.
Cyanide poisoning may occur subsequent to its use in the fetus.
Therefore, sodium nitroprusside should be reserved for use in
postpartum care or for administration just before the delivery of
the fetus.[8]Fluid ManagementLittle clinical evidence exists in the
published literature on which to base decisions regarding the
management of fluids during preeclampsia. Currently, no prospective
studies on this topic are available, and guidelines are largely
based on consensus and retrospective review.Despite the presence of
peripheral edema, patients with preeclampsia are intravascularly
volume depleted, with high peripheral vascular resistance.
Diuretics should be avoided.Aggressive volume resuscitation may
lead to pulmonary edema, which is a common cause of maternal
morbidity and mortality. Pulmonary edema occurs most frequently
48-72 hours postpartum, probably due to mobilization of
extravascular fluid. Because volume expansion has no demonstrated
benefit, patients should be fluid restricted when possible, at
least until the period of postpartum diuresis.Volume expansion has
not been shown to reduce the incidence of fetal distress and should
be used judiciously.Central venous or pulmonary artery pressure
monitoring may be indicated in critical cases. A central venous
pressure (CVP) of 5 mm Hg in women with no heart disease indicates
sufficient intravascular volume, and maintenance fluids alone are
sufficient. Total fluids should generally be limited to 80 mL/h or
1 mL/kg/h.Careful measurement of fluid input and output is
advisable, particularly in the immediate postpartum period. Many
patients will have a brief (up to 6 h) period of oliguria following
delivery; this should be anticipated and not
overcorrected.Postpartum ManagementPreeclampsia resolves after
delivery. However, patients may still have an elevated BP
postpartum. Liver function tests and platelet counts must be
performed to document decreasing values prior to hospital
discharge. In addition, one third of seizures occur in the
postpartum period, most within 24 hours of delivery, and almost all
within 48 hours.[57]Therefore, magnesium sulfate seizure
prophylaxis is continued for 24 hours postpartum. (See Seizure
Treatment and Prophylaxis With Magnesium Sulfate.)Rarely, a patient
may have elevated liver enzymes, thrombocytopenia, and renal
insufficiency more than 72 hours after delivery. In these cases,
the possibility of hemolytic uremic syndrome (HUS) or thrombotic
thrombocytopenic purpura (TTP) must be considered. In such
situations, plasmapheresis, along with corticosteroid therapy, may
be of some benefit to such patients and must be discussed with
renal and hematology consultants.In addition, the use of
dexamethasone (10 mg IV q6-12h for 2 doses followed by 5 mg IV
q6-12h for 2 doses) has been proposed in the postpartum period to
restore platelet count to normal range in patients with persistent
thrombocytopenia.[58, 59]The effectiveness of this therapy in
preventing severe hemorrhage or ameliorating the disease course
needs further investigation.Elevated BP may be controlled with
nifedipine or labetalol postpartum. If a patient is discharged with
BP medication, reassessment and a BP check should be performed, at
the latest, 1 week after discharge. Unless a woman has undiagnosed
chronic hypertension, in most cases of preeclampsia, the BP returns
to baseline by 12 weeks postpartum.Eclampsia is common after
delivery and has occurred up to 6 weeks after delivery. Al-Safi et
al suggest that the first week after discharge is the most critical
period for the development of postpartum eclampsia. Discussing the
risks and educating patients about the possibility of delayed
postpartum preeclampsia is important, regardless of whether they
develop hypertensive disease prior to discharge.[60]Patients at
risk for eclampsia should be carefully monitored
postpartum.[61]Additionally, patients with preeclampsia who were
successfully treated with delivery may present with recurrent
preeclampsia up to 4 weeks postpartum.Prevention and Prediction of
PreeclampsiaEfforts to prevent preeclampsia have been
disappointing.[62]AspirinA systematic review of 14 trials using
low-dose aspirin (60-150 mg/d) in women with risk factors for
preeclampsia concluded that aspirin reduced the risk of
preeclampsia and perinatal death, although it did not significantly
affect birth weight or the risk of abruption.[63]Low-dose aspirin
in unselected nulliparous women seems to reduce the incidence of
preeclampsia only slightly.[64]For women with risk factors for
preeclampsia, starting low-dose aspirin (commonly, 1 tablet of baby
aspirin per day), beginning at 12-14 weeks' gestation, is
reasonable. The safety of low-dose aspirin use in the second and
third trimesters is well established.[63, 65]HeparinThe use of
lowmolecular weight heparin in women with thrombophilia who have a
history of adverse outcome has been investigated. To date, however,
no data suggest that the use of heparin prophylaxis lowers the
incidence of preeclampsia.Calcium and vitamin supplementsResearch
into the use of calcium and vitamin C and E supplementations in
low-risk populations did not find a reduction in the incidence of
preeclampsia.[66, 67, 68]In a multicenter, randomized, controlled
trial, Villar et al found that at the doses used for
supplementation, vitamins C and E were not associated with a
reduction of preeclampsia, eclampsia, gestational hypertension, or
any other maternal outcome. Low birthweight, small for gestational
age, and perinatal deaths were also unaffected.[69]A study by
Vadillo-Ortega et al suggests that in a high-risk population,
supplementation during pregnancy with a special food (eg, bars)
containing L-arginine and antioxidant vitamins may reduce the risk
of preeclampsia. However, antioxidant vitamins alone do not protect
against preeclampsia. More studies performed on low-risk
populations are needed.[70]Results from the Norwegian Mother and
Child Cohort Study suggest that supplementation of milk-based
probiotics may reduce the risk of preeclampsia in primiparous
women. A prospective randomized trial has not yet been done to
evaluate this intervention.[71]Screening TestsPreeclampsia is an
appropriate disease to screen, as it is common, important, and
increases maternal and perinatal mortality. However, although
numerous screening tests for preeclampsia have been proposed over
the past few decades, no test has so far been shown to
appropriately screen for the disease.[72](Measurement of urinary
kallikrein was shown to have a high predictive value, but it was
not reproducible.[73, 74])Although work on sFlt-1, PlGF, and VEGF
have been promising, their positive predictive value in predicting
preeclampsia have yet to be evaluated in a prospective
fashion.Currently, the clinical value of an accurate predictive
test for preeclampsia is not clear, as effective prevention is
still lacking. Intensive monitoring in women who are at increased
risk for developing preeclampsia, when identified by a predictive
test, may lower the incidence of adverse outcome for the mother and
the neonate. However, the effectiveness of such a strategy must be
rigorously investigated.PrognosisMorbidity and mortalityWorldwide,
preeclampsia and eclampsia are estimated to be responsible for
approximately 14% of maternal deaths per year
(50,000-75,000).[16]Morbidity and mortality in preeclampsia and
eclampsia are related to the following conditions: Systemic
endothelial dysfunction Vasospasm and small-vessel thrombosis
leading to tissue and organ ischemia CNS events, such as seizures,
strokes, and hemorrhage Acute tubular necrosis Coagulopathies
Placental abruption in the motherRecurrenceIn general, the
recurrence risk of preeclampsia in a woman whose previous pregnancy
was complicated by preeclampsia near term is approximately
10%.[43]If a woman has previously suffered from severe preeclampsia
(including HELLP syndrome and/or eclampsia), she has a 20% risk of
developing preeclampsia sometime in her subsequent pregnancy.[75,
76, 77, 78, 79, 80]If a woman has had HELLP syndrome or eclampsia,
the recurrence risk of HELLP syndrome is 5%[76]and of eclampsia it
is 2%.[78, 79, 80]The earlier the disease manifests during the
index pregnancy, the higher the chance of recurrence rises. If
preeclampsia presented clinically before 30 weeks' gestation, the
chance of recurrence may be as high as 40%.[81]The fullPIERS model
has been validated and was successful in predicting adverse
outcomes in advance; therefore, it is potentially able to influence
treatment choices before complications arise.[82]