Preeclampsia
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Pre-eclampsia is a disorder of
pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
characterized by the onset of
high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease there may be red blood cell breakdown, a low blood platelet count, impaired liver function, kidney dysfunction, swelling, shortness of breath due to fluid in the lungs, or visual disturbances. Pre-eclampsia increases the risk of undesirable outcomes for both the mother and the fetus. If left untreated, it may result in
seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...
s at which point it is known as
eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
. Risk factors for pre-eclampsia include
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
, prior hypertension, older age, and
diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
. It is also more frequent in a woman's first pregnancy and if she is carrying twins. The underlying mechanism involves abnormal formation of blood vessels in the placenta amongst other factors. Most cases are diagnosed before delivery. Commonly, pre-eclampsia continues into the period after delivery, then known as postpartum pre-eclampsia. Rarely, pre-eclampsia may begin in the period after delivery. While historically both high blood pressure and protein in the urine were required to make the diagnosis, some definitions also include those with hypertension and any associated organ dysfunction. Blood pressure is defined as high when it is greater than 140 mmHg systolic or 90 mmHg
diastolic Diastole ( ) is the relaxed phase of the cardiac cycle when the chambers of the heart are re-filling with blood. The contrasting phase is systole when the heart chambers are contracting. Atrial diastole is the relaxing of the atria, and ventricu ...
at two separate times, more than four hours apart in a woman after twenty weeks of pregnancy. Pre-eclampsia is routinely screened during
prenatal care Prenatal care, also known as antenatal care, is a type of preventive healthcare. It is provided in the form of medical checkups, consisting of recommendations on managing a healthy lifestyle and the provision of medical information such as materna ...
. Recommendations for prevention include:
aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
in those at high risk,
calcium supplementation Calcium supplements are salts of calcium used in a number of conditions. Supplementation is generally only required when there is not enough calcium in the diet. By mouth they are used to treat and prevent low blood calcium, osteoporosis, and ...
in areas with low intake, and treatment of prior hypertension with medications. In those with pre-eclampsia, delivery of the baby and
placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
is an effective treatment but full recovery can take days or weeks. When delivery becomes recommended depends on how severe the pre-eclampsia and how far along in pregnancy a woman is.
Blood pressure medication Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests that r ...
, such as
labetalol Labetalol is a medication used to treat high blood pressure and in long term management of angina. This includes essential hypertension, hypertensive emergencies, and hypertension of pregnancy. In essential hypertension it is generally less pref ...
and
methyldopa Methyldopa, sold under the brand name Aldomet among others, is a medication used for high blood pressure. It is one of the preferred treatments for high blood pressure in pregnancy. For other types of high blood pressure including hypertensive e ...
, may be used to improve the mother's condition before delivery.
Magnesium sulfate Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, ...
may be used to prevent eclampsia in those with severe disease. Bed rest and salt intake have not been found to be useful for either treatment or prevention. Pre-eclampsia affects 2–8% of pregnancies worldwide.
Hypertensive disorders of pregnancy Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
(which include pre-eclampsia) are one of the most common causes of death due to pregnancy. They resulted in 46,900 deaths in 2015. Pre-eclampsia usually occurs after 32 weeks; however, if it occurs earlier it is associated with worse outcomes. Women who have had pre-eclampsia are at increased risk of
heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
and
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
later in life. The word "eclampsia" is from the Greek term for lightning. The first known description of the condition was by
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history of ...
in the 5th century BC.


Signs and symptoms

Oedema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
(especially in the hands and face) was originally considered an important sign for a diagnosis of pre-eclampsia. However, because oedema is a common occurrence in pregnancy, its utility as a distinguishing factor in pre-eclampsia is not high.
Pitting edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
(unusual swelling, particularly of the hands, feet, or face, notable by leaving an indentation when pressed on) can be significant, and should be reported to a health care provider. In general, none of the signs of pre-eclampsia are specific, and even convulsions in pregnancy are more likely to have causes other than eclampsia in modern practice. Further, a symptom such as epigastric pain may be misinterpreted as heartburn. Common features of pre-eclampsia which are screened for during pre-natal visits include elevated blood pressure and excess protein in the urine. Diagnosis depends on finding a coincidence of several pre-eclamptic features, the final proof being their regression within the days and weeks after delivery.


Causes

There is no definitive known cause of pre-eclampsia, though it is likely related to a number of factors. Some of these factors include: * Abnormal
placentation Placentation refers to the formation, type and structure, or arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo, and in some instances to remov ...
(formation and development of the placenta) * Immunologic factors * Prior or existing maternal pathology—pre-eclampsia is seen more at a higher incidence in individuals with pre-existing
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, obesity, or
antiphospholipid antibody syndrome Antiphospholipid syndrome, or antiphospholipid antibody syndrome (APS or APLS), is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy- ...
or those with a history of pre-eclampsia * Dietary factors, e.g. calcium supplementation in areas where dietary calcium intake is low has been shown to reduce the risk of pre-eclampsia * Environmental factors, e.g. air pollution Those with long term
high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
have a risk 7 to 8 times higher than those without. Physiologically, research has linked pre-eclampsia to the following physiologic changes: alterations in the interaction between the maternal immune response and the placenta, placental injury,
endothelial The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
cell injury, altered vascular reactivity, oxidative stress, imbalance among
vasoactive A vasoactive substance is an endogenous agent or pharmaceutical drug that has the effect of either increasing or decreasing blood pressure and/or heart rate through its vasoactivity, that is, vascular activity (effect on blood vessels). By adju ...
substances, decreased intravascular volume, and disseminated intravascular coagulation. While the exact cause of pre-eclampsia remains unclear, there is strong evidence that a major cause predisposing a susceptible woman to pre-eclampsia is an abnormally implanted placenta. This abnormally implanted placenta may result in poor uterine and placental perfusion, yielding a state of hypoxia and increased oxidative stress and the release of anti-
angiogenic Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splittin ...
proteins along with inflammatory mediators into the maternal plasma. A major consequence of this sequence of events is generalized
endothelial The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
dysfunction. The abnormal implantation may stem from the maternal
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
's response to the placenta, specifically a lack of established
immunological tolerance in pregnancy Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign i ...
. Endothelial dysfunction results in hypertension and many of the other symptoms and complications associated with pre-eclampsia. Those with pre-eclampsia may have a lower risk of breast cancer. Abnormal
chromosome 19 Chromosome 19 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 19 spans more than 58.6 million base pairs, the building material of DNA. It is considered the most gene-rich chromosom ...
microRNA cluster ( C19MC) impairs extravillus
trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the p ...
cell invasion to the
spiral arteries Spiral arteries are small arteries which temporarily supply blood to the endometrium of the uterus during the luteal phase of the menstrual cycle. In histology, identifying the presence of these arteries is one of the most useful techniques in i ...
, causing high resistance, low blood flow, and low nutrient supply to the fetus.


Genetic factors

Despite a lack of knowledge on specific causal mechanisms of pre-eclampsia, there is strong evidence to suggest it results from both environmental and heritable factors. A 2005 study showed that women with a first-degree relative who had a pre-eclamptic birth are twice as likely to develop it themselves. Furthermore, men related to someone with affected birth have an increased risk of fathering a pre-eclamptic pregnancy. Fetuses affected by pre-eclampsia have a higher chance of later pregnancy complications including growth restriction, prematurity, and stillbirth. The onset of pre-eclampsia is thought to be caused by several complex interactions between genetics and environmental factors. Our current understanding of the specifically heritable cause involves an imbalance of angiogenic factors in the placenta.
Angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splitting ...
involves the growth of new blood vessels from existing vessels, and an imbalance during pregnancy can affect the vascularization, growth, and biological function of the fetus. The irregular expression of these factors is thought to be controlled by multiple loci on different chromosomes. Research on the topic has been limited because of the
heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...
nature of the disease. Maternal, paternal, and fetal genotypes all play a role as well as complex epigenetic factors such as whether the parents smoke, maternal age, sexual cohabitation, and obesity. Currently, there is very little understanding behind the mechanisms of these interactions. Due to the polygenic nature of pre-eclampsia, a majority of the studies that have been conducted thus far on the topic have utilized
genome-wide association studies In genomics, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any varian ...
. One known effector of pre-eclampsia is the fetal loci
FLT1 Vascular endothelial growth factor receptor 1 is a protein that in humans is encoded by the ''FLT1'' gene. Function ''FLT1'' is a member of VEGF receptor gene family. It encodes a receptor tyrosine kinase which is activated by VEGF-A, VEGF-B ...
. Located on
chromosome 13 Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 114 million base pairs (the building material of DNA) and represents between 3.5 and 4% of the total DNA ...
in the q12 region, FLT1 codes for Fms-like
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
1, an angiogenic factor expressed in fetal
trophoblasts The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the ...
. Angiogenic factors are crucial for vascular growth in the placenta. An FLT1 soluble isoform caused by a
splice variant Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be in ...
is sFLT1, which works as an antiangiogenic factor, reducing vascular growth in the placenta. A healthy, normotensive pregnancy is characterized by a balance between these factors. However, upregulation of this variant and overexpression of sFL1 can contribute to
endothelial dysfunction In vascular diseases, endothelial dysfunction is a systemic pathological state of the endothelium. Along with acting as a semi-permeable membrane, the endothelium is responsible for maintaining vascular tone and regulating oxidative stress by ...
. Reduced vascular growth and endothelial dysfunction manifest primarily in maternal symptoms such as renal failure,
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's Tissue (biology), tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels t ...
, and seizures. However, these factors can also lead to inadequate oxygen, nutrient, or blood supply to the fetus. Furthermore, in this loci region, several
single-nucleotide polymorphism In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently lar ...
s (SNPs) have been observed to impact the overexpression of sFL1. Specifically, SNPs rs12050029 and rs4769613's risk alleles are linked with low red blood cell counts and carry an increased risk of late-onset pre-eclampsia.
Patau syndrome Patau syndrome is a syndrome caused by a chromosome, chromosomal abnormality, in which some or all of the Cell (biology), cells of the body contain Trisomy, extra genetic material from chromosome 13 (human), chromosome 13. The extra genetic mater ...
, or Trisomy 13, is also associated with the upregulation of sFLT1 due to the extra copy of the 13th chromosome. Because of this upregulation of an antiangiogenic factor, women with trisomy 13 pregnancies often experience reduced placental vascularization and are at higher risk for developing pre-eclampsia. Beyond fetal loci, there have been some maternal loci identified as effectors of pre-eclampsia.
Alpha-ketoglutarate-dependent hydroxylase Alpha-ketoglutarate-dependent hydroxylases are a major class of non-heme iron proteins that catalyse a wide range of reactions. These reactions include hydroxylation reactions, demethylations, ring expansions, ring closures, and desaturations. Func ...
expression on
chromosome 16 Chromosome 16 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 16 spans about 90 million base pairs (the building material of DNA) and represents just under 3% of the total DNA in cell ...
in the q12 region is also associated with pre-eclampsia. Specifically, allele rs1421085 heightens the risk of not just pre-eclampsia but also an increase in BMI and hypertension. This pleiotropy is one of the reasons why these traits are considered to be a risk factor. Furthermore,
ZNF831 Zinc finger protein 831 is a protein that in humans is encoded by the ZNF831 gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''b ...
(zinc finger protein 831) and its loci on chromosome 20q13 were identified as another significant factor in pre-eclampsia. The risk allele rs259983 is also associated with both pre-eclampsia and hypertension, further evidence that the two traits are possibly linked. While the current understanding suggests that maternal alleles are the main hereditary cause of pre-eclampsia, paternal loci have also been implicated. In one study, paternal
DLX5 Homeobox protein DLX-5 is a protein that in humans is encoded by the distal-less homeobox 5 gene, or ''DLX5'' gene. DLX5 is a member of DLX gene family. Function This gene encodes a member of a homeobox transcription factor gene family similar ...
(Distal-Less Homeobox 5) was identified as an imprinted gene. Located on
chromosome 7 Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 159 million base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total D ...
in the q21 region, DLX5 serves as a transcription factor often linked with the developmental growth of organs. When paternally inherited, DLX5 and its SNP rs73708843 are shown to play a role in trophoblast proliferation, affecting vascular growth and nutrient delivery. Besides specific loci, several important genetic regulatory factors contribute to the development of pre-eclampsia. Micro RNAs, or
miRNAs MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miR ...
, are noncoding mRNAs that down-regulate posttranscriptional gene expression through RNA-induced silencing complexes. In the placenta, miRNAs are crucial for regulating cell growth, angiogenesis, cell proliferation, and metabolism. These placental-specific miRNAs are clustered in large groups, mainly on chromosomes 14 and 19, and irregular expression of either is associated with an increased risk of an affected pregnancy. For instance, miR-16 and miR-29 are
vascular endothelial growth factors Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...
(VEGFs) and play a role in upregulating sFLT-1. In particular, the overexpression of miRNA miR-210 has been shown to induce hypoxia, which affects spiral artery remodeling, an important part of the pathogenesis of pre-eclampsia.


Risk factors

Known risk factors for pre-eclampsia include: * Having never previously given birth *
Diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
*
Kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an inflammatory kidney disease and has several types according to the location of the inflammation. Inflammation can ...
* Chronic hypertension * Prior history of pre-eclampsia * Family history of pre-eclampsia * Advanced maternal age (>35 years) * Obesity *
Antiphospholipid antibody syndrome Antiphospholipid syndrome, or antiphospholipid antibody syndrome (APS or APLS), is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy- ...
*
Multiple gestation A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such bi ...
* Having donated a kidney * Having sub-clinical hypothyroidism or
thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...
antibodies * Placental abnormalities such as placental
ischemia Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...


Pathogenesis

Although much research into mechanism of pre-eclampsia has taken place, its exact pathogenesis remains uncertain. Pre-eclampsia is thought to result from an abnormal placenta, the removal of which ends the disease in most cases. During normal pregnancy, the placenta vascularizes to allow for the exchange of water, gases, and solutes, including nutrients and wastes, between maternal and fetal circulations. Abnormal development of the placenta leads to poor placental perfusion. The placenta of women with pre-eclampsia is abnormal and characterized by poor trophoblastic invasion. It is thought that this results in oxidative stress, hypoxia, and the release of factors that promote endothelial dysfunction, inflammation, and other possible reactions. The clinical manifestations of pre-eclampsia are associated with general endothelial dysfunction, including vasoconstriction and end-organ
ischemia Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...
. Implicit in this generalized endothelial dysfunction may be an imbalance of
angiogenic Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splittin ...
and
anti-angiogenic An angiogenesis inhibitor is a substance that inhibits the growth of new blood vessels ( angiogenesis). Some angiogenesis inhibitors are endogenous and a normal part of the body's control and others are obtained exogenously through pharmaceutical d ...
factors. Both circulating and placental levels of
soluble fms-like tyrosine kinase-1 Soluble fms-like tyrosine kinase-1 (sFlt-1 or sVEGFR-1) is a tyrosine kinase protein with antiangiogenic properties. A non-membrane associated splice variant of VEGF receptor 1 (Flt-1), sFlt-1 binds the angiogenic factors VEGF (vascular endotheli ...
(sFlt-1) are higher in women with pre-eclampsia than in women with normal pregnancy. sFlt-1 is an anti-angiogenic protein that antagonizes
vascular endothelial growth factor Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...
(VEGF) and
placental growth factor Placental growth factor (PlGF) is a protein that in humans is encoded by the ''PGF'' gene. Placental growth factor (PGF) is a member of the VEGF (vascular endothelial growth factor) sub-family - a key molecule in angiogenesis and vasculogenesis, ...
(PIGF), both of which are proangiogenic factors. Soluble
endoglin Endoglin (ENG) is a type I membrane glycoprotein located on cell surfaces and is part of the TGF beta receptor complex. It is also commonly referred to as CD105, END, FLJ41744, HHT1, ORW and ORW1. It has a crucial role in angiogenesis, therefor ...
(sEng) has also been shown to be elevated in women with pre-eclampsia and has anti-angiogenic properties, much like sFlt-1 does. Both sFlt-1 and sEng are upregulated in all pregnant women to some extent, supporting the idea that hypertensive disease in pregnancy is a normal pregnancy adaptation gone awry. As natural killer cells are intimately involved in placentation and placentation involves a degree of
maternal immune tolerance Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign i ...
for a foreign placenta, it is not surprising that the maternal immune system might respond more negatively to the arrival of some placentae under certain circumstances, such as a placenta which is more invasive than normal. Initial maternal rejection of the placental cytotrophoblasts may be the cause of the inadequately remodeled
spiral arteries Spiral arteries are small arteries which temporarily supply blood to the endometrium of the uterus during the luteal phase of the menstrual cycle. In histology, identifying the presence of these arteries is one of the most useful techniques in i ...
in those cases of pre-eclampsia associated with shallow implantation, leading to downstream hypoxia and the appearance of maternal symptoms in response to upregulated sFlt-1 and sEng. Oxidative stress may also play an important part in the pathogenesis of pre-eclampsia. The main source of reactive oxygen species (ROS) is the enzyme
xanthine oxidase Xanthine oxidase (XO, sometimes XAO) is a form of xanthine oxidoreductase, a type of enzyme that generates reactive oxygen species. These enzymes catalyze the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthin ...
(XO) and this enzyme mainly occurs in the liver. One hypothesis is that the increased purine catabolism from placental hypoxia results in increased ROS production in the maternal liver and release into the maternal circulation that causes endothelial cell damage. Abnormalities in the maternal
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
and insufficiency of
gestational immune tolerance Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign i ...
seem to play major roles in pre-eclampsia. One of the main differences found in pre-eclampsia is a shift toward Th1 responses and the production of
IFN-γ Interferon gamma (IFN-γ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock ...
. The origin of IFN-γ is not clearly identified and could be the
natural killer cell Natural killer cells, also known as NK cells or large granular lymphocytes (LGL), are a type of cytotoxic lymphocyte critical to the innate immune system that belong to the rapidly expanding family of known innate lymphoid cells (ILC) and repres ...
s of the uterus, the placental dendritic cells modulating responses of
T helper cells The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...
, alterations in synthesis of or response to regulatory molecules, or changes in the function of
regulatory T cell The regulatory T cells (Tregs or Treg cells), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease. Treg cells are immunosu ...
s in pregnancy. Aberrant immune responses promoting pre-eclampsia may also be due to an altered fetal allorecognition or to inflammatory triggers. It has been documented that fetal cells such as fetal
erythroblasts A nucleated red blood cell (NRBC), also known by several other names, is a red blood cell that contains a cell nucleus. Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of t ...
as well as
cell-free fetal DNA Cell-free fetal DNA (cffDNA) is fetal DNA that circulates freely in the maternal blood. Maternal blood is sampled by venipuncture. Analysis of cffDNA is a method of non-invasive prenatal diagnosis frequently ordered for pregnant women of advance ...
are increased in the maternal circulation in women who develop pre-eclampsia. These findings have given rise to the hypothesis that pre-eclampsia is a disease process by which a placental lesion such as hypoxia allows increased fetal material into the maternal circulation, that in turn leads to an
immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...
and endothelial damage, and that ultimately results in pre-eclampsia and eclampsia. One hypothesis for vulnerability to pre-eclampsia is the maternal-fetal conflict between the maternal organism and fetus. After the first trimester trophoblasts enter the spiral arteries of the mother to alter the spiral arteries and thereby gain more access to maternal nutrients. Occasionally there is impaired trophoblast invasion that results in inadequate alterations to the uterine spiral arteries. It is hypothesized that the developing embryo releases biochemical signals that result in the woman developing hypertension and pre-eclampsia so that the fetus can benefit from a greater amount of maternal circulation of nutrients due to increased blood flow to the impaired placenta. This results in a conflict between maternal and fetal fitness and survival because the fetus is invested in only its survival and fitness while the mother is invested in this and subsequent pregnancies. Another evolutionary hypothesis for vulnerability to pre-eclampsia is the idea of ensuring pair-bonding between the mother and father and paternal investment in the fetus. Researchers posit that pre-eclampsia is an adaptation for the mother to terminate investment in a fetus that might have an unavailable father, as determined by repeated semen exposure of the father to the mother. Various studies have shown that women who frequently had exposure to partners' semen before conception had a reduced risk of pre-eclampsia. Also, subsequent pregnancies by the same father had a reduced risk of pre-eclampsia while subsequent pregnancies by a different father had a higher risk of developing pre-eclampsia. In normal early embryonic development, the outer epithelial layer contains cytotrophoblast cells, a stem cell type found in the trophoblast that later differentiates into the fetal placenta. These cells differentiate into many placental cells types, including extravillous trophoblast cells. Extravillous trophoblast cells are an invasive cell type which remodel the maternal spiral arteries by replacing the maternal epithelium and smooth muscle lining the spiral arteries causing artery dilation. This prevents maternal vasoconstriction in the spiral arteries and allows for continued blood and nutrient supply to the growing fetus with low resistance and high blood flow. In pre-eclampsia, abnormal expression of chromosome 19 microRNA cluster (C19MC) in placental cell lines reduces extravillus trophoblast migration. Specific microRNAs in this cluster which might cause abnormal spiral artery invasion include miR-520h, miR-520b, and 520c-3p. This impairs extravillus trophoblast cells invasion to the maternal spiral arteries, causing high resistance and low blood flow and low nutrient supply to the fetus. There is tentative evidence that vitamin supplementation can decrease the risk. Immune factors may also play a role.


Diagnosis

Testing for pre-eclampsia is recommended throughout
pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
via measuring a woman's blood pressure.


Diagnostic criteria

Pre-eclampsia is diagnosed when a pregnant woman develops: * Blood pressure ≥140 mmHg systolic or ≥90 mmHg diastolic on two separate readings taken at least four to six hours apart after 20 weeks' gestation in an individual with previously normal blood pressure. * In a woman with essential hypertension beginning before 20 weeks' gestational age, the diagnostic criteria are an increase in systolic blood pressure (SBP) of ≥30 mmHg or an increase in diastolic blood pressure (DBP) of ≥15 mmHg. *
Proteinuria Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy (although this symptom ma ...
≥ or more of protein in a 24-hour urine sample or a SPOT urinary protein to creatinine ratio ≥0.3 or a urine dipstick reading of 1+ or greater (dipstick reading should only be used if other quantitative methods are not available). Suspicion for pre-eclampsia should be maintained in any pregnancy complicated by elevated blood pressure, even in the absence of proteinuria. Ten percent of individuals with other signs and symptoms of pre-eclampsia and 20% of individuals diagnosed with eclampsia show no evidence of proteinuria. In the absence of proteinuria, the presence of new-onset
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
(elevated blood pressure) and the new onset of one or more of the following is suggestive of the diagnosis of pre-eclampsia: * Evidence of kidney dysfunction (
oliguria Oliguria or hypouresis is the low output of urine specifically more than 80 ml/day but less than 400ml/day.Boon et al, Davidson's Principles & Practice of Medicine (20th Ed), p475 The decreased output of urine may be a sign of dehydration, kidney ...
, elevated
creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an importa ...
levels) * Impaired liver function (noted by
liver function tests Liver function tests (LFTs or LFs), also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient's liver. These tests include prothrombin time (PT/INR), activated partial thromboplastin ti ...
) *
Thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients an ...
(platelet count <100,000/microliter) *
Pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive edema, liquid accumulation in the parenchyma, tissue and pulmonary alveolus, air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia an ...
* Ankle edema (pitting type) * Cerebral or visual disturbances Pre-eclampsia is a progressive disorder and these signs of organ dysfunction are indicative of severe pre-eclampsia. A systolic blood pressure ≥160 or diastolic blood pressure ≥110 and/or proteinuria >5g in a 24-hour period is also indicative of severe pre-eclampsia. Clinically, individuals with severe pre-eclampsia may also present
epigastric In anatomy, the epigastrium (or epigastric region) is the upper central region of the abdomen. It is located between the costal margins and the subcostal plane. Pain may be referred to the epigastrium from damage to structures derived from the f ...
/right upper quadrant abdominal pain, headaches, and vomiting. Severe pre-eclampsia is a significant risk factor for intrauterine fetal death. A rise in baseline blood pressure (BP) of 30 mmHg systolic or 15 mmHg diastolic, while not meeting the absolute criteria of 140/90, is important to note but is not considered diagnostic.


Predictive tests

There have been many assessments of tests aimed at predicting pre-eclampsia, though no single biomarker is likely to be sufficiently predictive of the disorder. Predictive tests that have been assessed include those related to placental perfusion, vascular resistance, kidney dysfunction,
endothelial The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
dysfunction, and oxidative stress. Examples of notable tests include: * Doppler
ultrasonography Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...
of the uterine arteries to investigate for signs of inadequate placental perfusion. This test has a high negative predictive value among those individuals with a history of prior pre-eclampsia. * Elevations in serum uric acid (
hyperuricemia Hyperuricaemia or hyperuricemia is an abnormally high level of uric acid in the blood. In the pH conditions of body fluid, uric acid exists largely as urate, the ion form. Serum uric acid concentrations greater than 6 mg/dL for females, 7&nbs ...
) is used by some to "define" pre-eclampsia, though it has been found to be a poor predictor of the disorder. Elevated levels in the blood (
hyperuricemia Hyperuricaemia or hyperuricemia is an abnormally high level of uric acid in the blood. In the pH conditions of body fluid, uric acid exists largely as urate, the ion form. Serum uric acid concentrations greater than 6 mg/dL for females, 7&nbs ...
) are likely due to reduced uric acid clearance secondary to impaired kidney function. *
Angiogenic Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splittin ...
proteins such as
vascular endothelial growth factor Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...
(VEGF) and
placental growth factor Placental growth factor (PlGF) is a protein that in humans is encoded by the ''PGF'' gene. Placental growth factor (PGF) is a member of the VEGF (vascular endothelial growth factor) sub-family - a key molecule in angiogenesis and vasculogenesis, ...
(PIGF) and anti-angiogenic proteins such as
soluble fms-like tyrosine kinase-1 Soluble fms-like tyrosine kinase-1 (sFlt-1 or sVEGFR-1) is a tyrosine kinase protein with antiangiogenic properties. A non-membrane associated splice variant of VEGF receptor 1 (Flt-1), sFlt-1 binds the angiogenic factors VEGF (vascular endotheli ...
(sFlt-1) have shown promise for potential clinical use in diagnosing pre-eclampsia, though evidence is insufficient to recommend a clinical use for these markers. A recent study, ASPRE, known to be the largest multi-country prospective trial, has reported a significant performance in identifying pregnant women at high risk of pre-eclampsia yet during the first trimester of pregnancy. Utilizing a combination of maternal history, mean arterial blood pressure, intrauterine Doppler and PlGF measurement, the study has shown a capacity to identify more than 75% of the women that will develop pre-eclampsia, allowing early intervention to prevent development of later symptoms. This approach is now officially recommended by the International Federation of Gynecologists & Obstetricians (FIGO) * Recent studies have shown that looking for
podocyte Podocytes are cells in Bowman's capsule in the kidneys that wrap around capillaries of the glomerulus. Podocytes make up the epithelial lining of Bowman's capsule, the third layer through which filtration of blood takes place. Bowman's capsule ...
s (specialized cells of the kidney) in the urine has the potential to aid in the prediction of pre-eclampsia. Studies have demonstrated that finding podocytes in the urine may serve as an early marker of and diagnostic test for pre-eclampsia.


Differential diagnosis

Pre-eclampsia can mimic and be confused with many other diseases, including chronic hypertension, chronic renal disease, primary seizure disorders, gallbladder and
pancreatic disease Pancreatic diseases are diseases that affect the pancreas, an organ in most vertebrates and in humans and other mammals located in the abdomen. The pancreas plays a role in the digestive and endocrine system, producing enzymes which aid the digesti ...
, immune or
thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, h ...
,
antiphospholipid syndrome Antiphospholipid syndrome, or antiphospholipid antibody syndrome (APS or APLS), is an autoimmune, hypercoagulable state caused by antiphospholipid antibodies. APS provokes blood clots (thrombosis) in both arteries and veins as well as pregnancy-r ...
and hemolytic-uremic syndrome. It must be considered a possibility in any pregnant woman beyond 20 weeks of gestation. It is particularly difficult to diagnose when pre-existing conditions such as
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
are present. Women with
acute fatty liver of pregnancy Acute fatty liver of pregnancy is a rare life-threatening complication of pregnancy that occurs in the third trimester or the immediate period after delivery. It is thought to be caused by a disordered metabolism of fatty acids by mitochondria in ...
may also present with elevated blood pressure and protein in the urine, but differ by the extent of liver damage. Other disorders that can cause high blood pressure include
thyrotoxicosis Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. ...
,
pheochromocytoma Pheochromocytoma (PHEO or PCC) is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred t ...
, and
drug misuse Substance abuse, also known as drug abuse, is the use of a drug in amounts or by methods which are harmful to the individual or others. It is a form of substance-related disorder. Differing definitions of drug abuse are used in public health, ...
.


Prevention

Preventive measures against pre-eclampsia have been heavily studied. Because the pathogenesis of pre-eclampsia is not completely understood, prevention remains a complex issue. Some currently accepted recommendations are:


Diet

Supplementation with a balanced protein and energy diet does not appear to reduce the risk of pre-eclampsia. Further, there is no evidence that changing
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
intake has an effect. Supplementation with
antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...
s such as
vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) an ...
, D and E has no effect on pre-eclampsia incidence; therefore, supplementation with vitamins C, E, and D is not recommended for reducing the risk of pre-eclampsia.
Calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
supplementation of at least 1 gram per day is recommended during pregnancy as it prevents pre-eclampsia where dietary calcium intake is low, especially for those at high risk. Higher
selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
level is associated with lower incidence of pre-eclampsia. Higher
cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
level is associated with higher incidence of pre-eclampsia.


Aspirin

Taking
aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
is associated with a 1 to 5% reduction in pre-eclampsia and a 1 to 5% reduction in premature births in women at high risk. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
recommends low-dose aspirin for the prevention of pre-eclampsia in women at high risk and recommends it be started before 20 weeks of pregnancy. The
United States Preventive Services Task Force The United States Preventive Services Task Force (USPSTF) is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services". ...
recommends a low-dose regimen for women at high risk beginning in the 12th week. Benefits are less if started after 16 weeks. The more recent study ASPRE, besides its efficacy in identifying women suspected to develop pre-eclampsia, has also been able to demonstrate a strong drop in the rate of early pre-eclampsia (-82%) and preterm pre-eclampsia (-62%). The efficacy of aspirin is due to screening to identify high risk women, adjusted prophylaxis dosage (150 mg/day), timing of the intake (bedtime) and must start before week 16 of pregnancy.


Physical activity

There is insufficient evidence to recommend either exercise or strict bedrest as preventive measures of pre-eclampsia.


Smoking cessation

In low-risk pregnancies, the association between cigarette
smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...
and a reduced risk of pre-eclampsia has been consistent and reproducible across epidemiologic studies. High-risk pregnancies (those with pregestational diabetes, chronic hypertension, history of pre-eclampsia in a previous pregnancy, or multifetal gestation) showed no significant protective effect. The reason for this discrepancy is not definitively known; research supports speculation that the underlying pathology increases the risk of pre-eclampsia to such a degree that any measurable reduction of risk due to smoking is masked. However, the damaging effects of smoking on overall health and pregnancy outcomes outweighs the benefits in decreasing the incidence of pre-eclampsia. It is recommended that smoking be stopped prior to, during and after pregnancy.


Immune modulation

Some studies have suggested the importance of a woman's gestational immunological tolerance to her baby's father, as the baby and father share genetics. There is tentative evidence that ongoing exposure either by vaginal or oral sex to the same semen that resulted in the pregnancy decreases the risk of pre-eclampsia. As one early study described, "although pre-eclampsia is a disease of first pregnancies, the protective effect of multiparity is lost with change of partner". The study also concluded that although women with changing partners are strongly advised to use condoms to prevent sexually transmitted diseases, "a certain period of sperm exposure within a stable relation, when pregnancy is aimed for, is associated with protection against pre-eclampsia". Several other studies have since investigated the decreased incidence of pre-eclampsia in women who had received blood transfusions from their partner, those with long preceding histories of sex without barrier contraceptives, and in women who had been regularly performing
oral sex Oral sex, sometimes referred to as oral intercourse, is sexual activity involving the stimulation of the genitalia of a person by another person using the mouth (including the lips, tongue, or teeth) and the throat. Cunnilingus is oral sex per ...
. Having already noted the importance of a woman's immunological tolerance to her baby's paternal genes, several Dutch reproductive biologists decided to take their research a step further. Consistent with the fact that human immune systems tolerate things better when they enter the body via the mouth, the Dutch researchers conducted a series of studies that confirmed a surprisingly strong correlation between a diminished incidence of pre-eclampsia and a woman's practice of oral sex, and noted that the protective effects were strongest if she swallowed her partner's semen. A team from the
University of Adelaide The University of Adelaide (informally Adelaide University) is a public research university located in Adelaide, South Australia. Established in 1874, it is the third-oldest university in Australia. The university's main campus is located on N ...
has also investigated to see if men who have fathered pregnancies which have ended in
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical lo ...
or pre-eclampsia had low seminal levels of critical immune modulating factors such as
TGF-beta Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...
. The team has found that certain men, dubbed "dangerous males", are several times more likely to father pregnancies that would end in either pre-eclampsia or miscarriage. Among other things, most of the "dangerous males" seemed to lack sufficient levels of the seminal immune factors necessary to induce
immunological tolerance Immune tolerance, or immunological tolerance, or immunotolerance, is a state of unresponsiveness of the immune system to substances or tissue that would otherwise have the capacity to elicit an immune response in a given organism. It is induced by ...
in their partners. As the theory of immune intolerance as a cause of pre-eclampsia has become accepted, women who with repeated pre-eclampsia, miscarriages, or
in vitro fertilization In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating an individual's ovulatory process, removing an ovum or ova (egg or eggs) ...
failures could potentially be administered key immune factors such as TGF-beta along with the father's foreign proteins, possibly either orally, as a sublingual spray, or as a vaginal gel to be applied onto the vaginal wall before intercourse.


Treatment

The definitive treatment for pre-eclampsia is the delivery of the baby and placenta, but danger to the mother persists after delivery, and full recovery can take days or weeks. The timing of delivery should balance the desire for optimal outcomes for the baby while reducing risks for the mother. The severity of disease and the maturity of the baby are primary considerations. These considerations are situation-specific and management will vary with situation, location, and institution. Treatment can range from expectant management to expedited delivery by
induction of labor Labor induction is the process or treatment that stimulates childbirth and delivery. Inducing (starting) labor can be accomplished with pharmaceutical or non-pharmaceutical methods. In Western countries, it is estimated that one-quarter of pregnan ...
or
Caesarean section Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or mo ...
, in addition to medications. Important in management is the assessment of the mother's organ systems, management of severe hypertension, and prevention and treatment of eclamptic seizures. Separate interventions directed at the baby may also be necessary. Bed rest has not been found to be useful and is thus not routinely recommended.


Blood pressure

The World Health Organization recommends that women with severe
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
during pregnancy should receive treatment with anti-hypertensive agents. Severe hypertension is generally considered systolic BP of at least 160 or diastolic BP of at least 110. Evidence does not support the use of one anti-hypertensive over another. The choice of which agent to use should be based on the prescribing clinician's experience with a particular agent, its cost, and its availability. Diuretics are not recommended for prevention of pre-eclampsia and its complications.
Labetalol Labetalol is a medication used to treat high blood pressure and in long term management of angina. This includes essential hypertension, hypertensive emergencies, and hypertension of pregnancy. In essential hypertension it is generally less pref ...
,
hydralazine Hydralazine, sold under the brand name Apresoline among others, is a medication used to treat high blood pressure and heart failure. This includes high blood pressure in pregnancy and very high blood pressure resulting in symptoms. It has been ...
and
nifedipine Nifedipine (3,5-dimethyl 2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate), sold under the brand name Adalat and Procardia, among others, is a calcium channel blocker medication used to manage angina, high blood pressure, Ra ...
are commonly used antihypertensive agents for
hypertension in pregnancy ''Hypertension in Pregnancy'' is a quarterly peer-reviewed medical journal covering human and animal hypertension during gestation, including the physiology of circulatory control, pathophysiology, methodology, and therapy. It is published by ...
.
ACE inhibitor Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
s and
angiotensin receptor blockers Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT1) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT1 receptor antagonists, are a group of pharmaceuticals tha ...
are contraindicated as they affect fetal development. The goal of treatment of severe hypertension in pregnancy is to prevent cardiovascular, kidney, and cerebrovascular complications. The target blood pressure has been proposed to be 140–160 mmHg systolic and 90–105 mmHg diastolic, although values are variable.


Prevention of eclampsia

The intrapartum and postpartum administration of magnesium sulfate is recommended in severe pre-eclampsia for the prevention of
eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
. Further, magnesium sulfate is recommended for the treatment of eclampsia over other anticonvulsants. Magnesium sulfate acts by interacting with NMDA receptors.


Epidemiology

Pre-eclampsia affects approximately 2–8% of all pregnancies worldwide. The incidence of pre-eclampsia has risen in the U.S. since the 1990s, possibly as a result of increased prevalence of predisposing disorders, such as chronic hypertension, diabetes, and obesity. Pre-eclampsia is one of the leading causes of maternal and perinatal morbidity and mortality worldwide. Nearly one-tenth of all maternal deaths in Africa and Asia and one-quarter in Latin America are associated with hypertensive diseases in pregnancy, a category that encompasses pre-eclampsia. Pre-eclampsia is much more common in women who are pregnant for the first time. Women who have previously been diagnosed with pre-eclampsia are also more likely to experience pre-eclampsia in subsequent pregnancies. Pre-eclampsia is also more common in women who have pre-existing
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
,
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
,
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
,
autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". ...
diseases such as
lupus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Comm ...
, various inherited thrombophilias such as
Factor V Leiden Factor V Leiden (rs6025 or ''F5'' p.R506Q) is a variant (mutated form) of human factor V (one of several substances that helps blood clot), which causes an increase in blood clotting (hypercoagulability). Due to this mutation, protein C, an anticoa ...
,
renal disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an inflammatory kidney disease and has several types according to the location of the inflammation. Inflammation can b ...
, multiple gestation (
twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
s or
multiple birth A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such bir ...
), and advanced maternal age. Women who live at high altitude are also more likely to experience pre-eclampsia. Pre-eclampsia is also more common in some ethnic groups (e.g. African-Americans, Sub-Saharan Africans, Latin Americans, African Caribbeans, and Filipinos). Change of paternity in a subsequent pregnancy has been implicated as affecting risk, except in those with a family history of hypertensive pregnancy.
Eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
is a major complication of pre-eclampsia. Eclampsia affects 0.56 per 1,000 pregnant women in developed countries and almost 10 to 30 times as many women in low-income countries as in developed countries.


Complications

Complications of pre-eclampsia can affect both the mother and the fetus. Acutely, pre-eclampsia can be complicated by
eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
, the development of
HELLP syndrome HELLP syndrome is a complication of pregnancy; the acronym stands for hemolysis, elevated liver enzymes, and low platelet count. It usually begins during the last three months of pregnancy or shortly after childbirth. Symptoms may include feelin ...
, hemorrhagic or ischemic
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
, liver damage and dysfunction,
acute kidney injury Acute kidney injury (AKI), previously called acute renal failure (ARF), is a sudden decrease in kidney function that develops within 7 days, as shown by an increase in serum creatinine or a decrease in urine output, or both. Causes of AKI are cla ...
, and
acute respiratory distress syndrome Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin colo ...
(ARDS). Pre-eclampsia is also associated with increased frequency of
Caesarean section Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or mo ...
, preterm delivery, and
placental abruption Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 Gestational age (obstetrics), weeks of pregnancy. Symptoms may include vaginal bleeding, lower ...
. Furthermore, an elevation in blood pressure can occur in some individuals in the first week postpartum attributable to volume expansion and fluid mobilization. Fetal complications include fetal growth restriction and potential fetal or perinatal death. Long-term, an individual with pre-eclampsia is at increased risk for recurrence of pre-eclampsia in subsequent pregnancies.


Eclampsia

Eclampsia Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
is the development of new convulsions in a pre-eclamptic patient that may not be attributed to other causes. It is a sign that the underlying pre-eclamptic condition is severe and is associated with high rates of perinatal and maternal morbidity and mortality. Warning symptoms for eclampsia in an individual with current pre-eclampsia may include headaches, visual disturbances, and right upper quadrant or epigastric abdominal pain, with a headache being the most consistent symptom. During pregnancy brisk or hyperactive reflexes are common, however ankle
clonus Clonus is a set of involuntary and rhythmic muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cas ...
is a sign of neuromuscular irritability that usually reflects severe pre-eclampsia and also can precede eclampsia.
Magnesium sulfate Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, ...
is used to prevent convulsions in cases of severe pre-eclampsia.


HELLP Syndrome

HELLP syndrome HELLP syndrome is a complication of pregnancy; the acronym stands for hemolysis, elevated liver enzymes, and low platelet count. It usually begins during the last three months of pregnancy or shortly after childbirth. Symptoms may include feelin ...
is defined as
hemolysis Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
(microangiopathic), elevated liver enzymes (liver dysfunction), and low platelets (
thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients an ...
). This condition may occur in 10–20% of patients with severe pre-eclampsia and eclampsia and is associated with increased maternal and fetal morbidity and mortality. In 50% of instances, HELLP syndrome develops preterm, while 20% of cases develop in late gestation and 30% during the post-partum period.


Long term

Preeclampsia predisposes for future cardiovascular disease and a history of preeclampsia/eclampsia doubles the risk for cardiovascular mortality later in life. Other risks include
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
,
chronic hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, kidney disease and
venous thromboembolism Venous thrombosis is blockage of a vein caused by a thrombus (blood clot). A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to ...
. Preeclampsia and cardiovascular disease share many risk factors such as age, elevated BMI, family history and certain chronic diseases. seems pre-eclampsia does not increase the risk of
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. Lowered blood supply to the fetus in pre-eclampsia causes lowered nutrient supply, which could result in
intrauterine growth restriction Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...
(IUGR) and low birth weight. The fetal origins hypothesis states that fetal undernutrition is linked with coronary heart disease later in adult life due to disproportionate growth. Because pre-eclampsia leads to a mismatch between the maternal energy supply and fetal energy demands, pre-eclampsia can lead to IUGR in the developing fetus. Infants with IUGR are prone to have poor neuronal development and in increased risk for adult disease according to the Barker hypothesis. Associated adult diseases of the fetus due to IUGR include, but are not limited to,
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pla ...
(CAD),
type 2 diabetes mellitus Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urinatio ...
(T2DM),
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
,
osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone ...
, and various psychiatric illnesses. The risk of pre-eclampsia and development of placental dysfunction has also been shown to be recurrent cross-generationally on the maternal side and most likely on the paternal side. Fetuses born to mothers who were born small for
gestational age In obstetrics, gestational age is a measure of the age of a pregnancy which is taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. Su ...
(SGA) were 50% more likely to develop pre-eclampsia while fetuses born to both SGA parents were three-fold more likely to develop pre-eclampsia in future pregnancies.


History

The word "eclampsia" is from the Greek term for
lightning Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
. The first known description of the condition was by
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history of ...
in the 5th century BC. An outdated medical term for pre-eclampsia is toxemia of pregnancy, a term that originated in the mistaken belief that the condition was caused by
toxins A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849–1 ...
.


References


External links

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MedlinePlus MedlinePlus is an online information service produced by the United States National Library of Medicine. The service provides curated consumer health information in English and Spanish with select content in additional languages. The site brings t ...
br>entry on high blood pressure in pregnancy
*
Mayo Clinic The Mayo Clinic () is a nonprofit American academic medical center focused on integrated health care, education, and research. It employs over 4,500 physicians and scientists, along with another 58,400 administrative and allied health staff, ...
br>fact sheet on pre-eclampsia
{{Pathology of pregnancy, childbirth and the puerperium Health issues in pregnancy Medical emergencies Rare diseases Wikipedia medicine articles ready to translate Women's health