Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2617_Библиотеки_им_академика_М_И_Перельмана
.pdf
30 The Role of Laboratory inPregnancy
https://t.me/medicina_free
425
Table 30.2
Result Avidity Interpretation
0–19% Weak Probable current or recent infection (not
20–30% Intermediate Probable recent infection
>30% Heavy Previous infection
Immunoglobulin G avidity test
more than 3 months)
IgM must be considered an alarm signal, but it is not a
specic indicator of the acute phase of the infection. IgMs
appear early, 10–12days after infection, and reach a plateau
after 2–4 weeks; in 72% of cases, they are still detectable
after 9–10months and can remain low titers for more than a
year. Serum IgM does not necessarily indicate an ongoing or
recent infection. However, it could be due to long-lasting
IgM or nonspecic “natural” IgM, produced independently
from the presence of Toxoplasma infection, recent or past,
and often detectable in the rst trimester of pregnancy. In
order to conrm and date toxoplasmosis, level II investigations
are performed, such as the IgA assay and the assessment of
IgG avidity. IgA is generally produced after IgM and before
IgG; initially, there is a rapid increase and subsequent
decrease by 6–9 months, earlier than IgM; they may reappear
after reactivation in the absence of IgM.The simultaneous
presence of IgA and IgM allows a fairly reliable diagnosis of
recent toxoplasmosis acquired in the last 6 months. The IgG
avidity test is the most reliable method to date the infection.
Avidity represents the strength of binding between an antibody and its antigen. The IgG avidity test, in general, is
based on the principle that IgG undergoes an increase in
antigen-binding afnity during the evolution of the immune
response, which diagnostically translates into an antigenantibody bond that is less sensitive to the action of a denaturing agent. Consequently, the closer the production of IgG in
time, the lower the strength of antigen binding and the lower
the avidity; this allows reliable dating of the infection. In
other words, IgG with low avidity is usually present during
the acute phase (Table30.2).
Others
Syphilis
Syphilis is an infectious disease caused by the Treponema
pallidum bacterium, transmitted mainly through sexual con-
tact but sometimes by the transplacental route and during
passage through the birth canal. Syphilis can therefore be
dened as:
• Acquired, when contracted after birth
• Congenital or prenatal, when contracted transplacentally
• Connatal, when acquired at the time of passage through
the birth canal
Syphilis develops in several stages, each characterized by
different symptoms and courses.
In the primary stage, after an incubation period of about
3weeks, a painless lump (a complicated ulcer or syphiloma)
appears at the point of inoculation of the bacterium (generally the genitals). Usually, the syphiloma disappears even if
it is not treated, but after 6weeks, if the disease is not treated,
it evolves into the secondary stage. The latter is characterized
by the invasion of the bacterium throughout the body, resulting in unaccompanied rashes, itching, fever, enlarged lymph
nodes, patchy alopecia, headache, weight loss, myalgia, and
fatigue. These skin manifestations disappear after 1–2weeks
but recur over the years (latent stage). Without appropriate
treatment, lesions in the internal organs, especially in the
central nervous system, may occur after years; in the tertiary
stage, the spinal cord will be affected (motor disorders), and
in the last stage, the brain (dementia).
Maternal–fetal transmission can occur at any time during
pregnancy, but the risk of transmission is most signicant
from the third month and increases as gestation progresses.
The stage of the mother’s syphilis is the most critical factor
in determining the probability of vertical transmission.
Primary or secondary syphilis, if untreated, carries a risk of
fetal transmission of 70–100%, if treated, 2%; in case of
early latent syphilis, 40–83%; and 2.5–10% in the late latent
infection stage.
Early treatment of the mother with penicillin theoretically
eliminates the risk of vertical transmission of the disease as
long as the interval between initiation of therapy and delivery is >4weeks. The severity of untreated fetal infection is
greater the earlier the infection. Therefore, prevention and
diagnosis of congenital syphilis depend on the infection’s
diagnosis and treatment in the pregnant woman.
The neonatal consequences of vertical transmission
include not only congenital syphilis, which is characterized
by developmental alterations in the child if left untreated, but
also obstetrical complications such as late abortion, death in
utero, fetal hydrops, and preterm delivery.
Two types of tests can be used for serological screening:
• Nonspecic treponema tests, based on the detection of
IgG and IgM antibodies directed against substances
released by the tissues due to the pathogenic action of
treponema, dened as antilipoid antibodies. Among these,
the most commonly used are the rapid plasma reagin
(RPR) and the venereal disease research laboratories
(VDRL).
• Treponema-specic tests, based on the detection of anti-
bodies to Treponema pallidum-specic antigens.
VDRL is a simple test based on a occulation reaction
between the patient’s serum and particular types of lipids,
426
https://t.me/medicina_free
M. Ciaccio and L. Agnello
known as cardiolipins. RPR is a technical variant of VDRL
in which the addition of micro carbon particles modies the
antigen. Both techniques are easy to perform, inexpensive,
and characterized by high sensitivity and low specicity; a
false-positive result can be observed in cases of infectious
diseases such as malaria, tuberculosis, viral fevers, trypanosomiasis, and leprosy and in other conditions such as pregnancy, collagenopathies, advanced age, and drug addiction.
Treponema-specic tests include the Treponema Pallidum
Haemagglutination Assay (TPHA) and the Treponema
Pallidum Particle Agglutination Assay (TPPA), which are
positive 2–4 weeks after infection and have a sensitivity
ranging from 60% to 99% (low sensitivity only at disease
onset) and a specicity >99%, and immunoassays, such as
the enzyme immunoassay (EIA) and the chemiluminescence
assay (CLIA). EIA (with recombinant antigens) is positive
3weeks after infection, with a sensitivity >98% and specicity >97%; CLIA is positive 3weeks after infection, with a
sensitivity and specicity >98% and >97%, respectively;
uorescent treponemal antibody absorption (an immunouorescence test with adsorption, currently little used) has a
sensitivity of 84% in primary syphilis and about 100% in the
other stages, and a specicity of 96%. While for nonspecic
tests, the titer of positivity correlates with disease activity
and response to therapy, treponema-specic tests generally
remain positive throughout life, regardless of therapy and
disease activity.
Syphilis in pregnancy is a largely preventable cause of
neonatal morbidity and mortality through screening and
treatment of the infection in the mother. Diagnosis and staging of syphilis in pregnant women are based on clinical
examination and serological testing. The serological screening test is a treponema-specic test (TPHA, TPPA, EIA, or
CLIA). A second specic test must conrm positivity ofone
specic test. If the diagnosis of syphilis is conrmed, a nonspecic test (RPR or VDRL) should be performed to determine the stage of infection.
Hepatitis
Acute infectious hepatitis can be caused by various types of
viruses (A-B-C-D-E) with hepatic tropism. Generally, from
a clinical point of view, hepatitis is asymptomatic or associated with nonspecic symptoms such as nausea, vomiting,
myalgia, and anorexia. While hepatitis A is not transmitted
from mother to fetus (to date, only two cases have been
reported), hepatitis B and C represent an important problem
for Public Health and can be transmitted vertically. The hepatitis B virus (HBV) is a DNA virus of the Hepadnaviridae
family that, after a long incubation period (1–6 months),
causes an acute infection, often asymptomatic, which rarely
evolves into fulminant hepatitis. The frequency of chronic
infection depends on the age at which it is acquired, being
low (1–5%) in adults and high in children (90%); all infants
who become infected in the perinatal period will develop a
chronic infection. In order to prevent vertical transmission of
HBV, it is necessary to identify women who carry the virus
by detecting the surface antigen (HbsAg) by serological
tests; if the test is positive, the result must be conrmed.
Then the search for “e” antigen (HBeAg), an index of active
virus replication, is performed to assess whether the newborn should be subjected to immunoprophylaxis and postnatal vaccination.
Hepatitis C virus (HCV) is a RNA virus associated with a
relatively low risk of vertical transmission (3–5%). The risk
of vertical transmission increases signicantly (up to
40–60%) if the mother is simultaneously infected with
HIV.Screening is performed by the detection of HCV antibodies using serological tests (enzyme-linked immunosorbent assay [ELISA]); a positive test must be conrmed by
another test. If positive, the diagnosis should be conrmed
by the identication of HCV-RNA by polymerase chain
reaction (PCR), which is the gold standard. Guidelines recommend prenatal screening for HCV only for women at risk.
Human Immunodeciency Virus
The human immunodeciency virus (HIV) is an RNA lentivirus with a reverse transcriptase that converts RNA to
DNA.The virus can be transmitted vertically by the transplacental route, during childbirth, and during lactation. Most
transmission episodes have been recorded during childbirth.
Early identication of HIV-seropositive women aims to
implement preventive measures to reduce the risk of maternal–fetal virus transmission. Preventive measures in HIVpositive women are associated with a 1% reduction in the
risk of maternal–fetal transmission and include a planned
cesarean section at 38weeks of gestational age, prophylaxis
with zidovudine (an antiviral drug), and articial breastfeeding. Screening is based on detecting HIV 1 and 2 antibodies
by ELISA. Since antibodies are detectable in the serum
about 3months after infection (the window period), a negative result does not exclude the presence of the infection. A
positive result must be conrmed by a more specic test
(Western blot). Infection in newborns is diagnosed through
the search for nucleic acid by PCR or viral antigen because
maternal antibodies can cross the placenta giving falsepositive results.
Rubella
Rubella is an infectious disease caused by an RNA virus
belonging to the Togaviridae family. The infection is generally contracted in childhood. In 1972, the vaccine was introduced in Italy, initially recommended only for girls in
puberty but later extended to all children of both sexes aged
<2years. Acute primary infections and vaccination result in
permanent immunity. If the infection is contracted during
pregnancy, it can cause severe damage to the fetus, such as
30 The Role of Laboratory inPregnancy
https://t.me/medicina_free
427
malformations or intrauterine death, because the virus can
reach the fetal circulation and multiply rapidly in the embryonic tissues, causing an alteration of organogenesis. Vertical
virus transmission can occur throughout gestation, with a
greater risk of transplacental passage in the rst trimester.
The objective of screening is to assess the mother’s immunity using the rubeotest (a serological test for detecting IgM
and IgG anti-rubella antibodies) to identify women susceptible to infection. If a woman is negative for rubella before
pregnancy, she can be vaccinated as a preventive measure.
Unfortunately, there is no therapy to reduce vertical
transmission, and the vaccine is not recommended during
pregnancy because it could be teratogenic.
Cytomegalovirus
Cytomegalovirus (CMV) is a DNA virus from the
Herpesviridae family. Humans are the only reservoir, and
transmission can occur horizontally, from human to human
by direct or indirect contact, or vertically, during pregnancy.
The virus is present in all body uids, including milk. Vertical
transmission can occur by the transplacental route, either by
primary infections (rst acquired), secondary infections
(reinfection or reactivation of latent virus), or by perinatal
route, either during birth or lactation. The risk of vertical
transmission is approximately 30–40% in primary infections
and 0.5–2% in secondary infections. Infants with congenital
infections are mostly(90%) asymptomatic, and a small percentage will present neurosensory alterations, such as mental
retardation, psychomotor retardation, hypotonia, autism,
hearing defects, and visual defects.
The diagnosis of CMV infection is based on serological
investigations aimed at identifying the presence of IgG and
IgM antibodies directed against CMV and the avidity of IgG
antibodies. In particular, the detection of serumvirus- specic
IgG in a previously seronegative woman or virus-specic
IgM associated with low-avidity IgG suggests a primary
infection. The diagnosis of secondary infection, on the other
hand, is based on the nding of an increased IgG antibody
titer, with or without high avidity IgM and IgG.In the case of
primary maternal infection, amniocentesis should be performed to assess whether the fetus is infected and to identify
the presence of the virus by searching for its DNA.However,
the diagnosis of fetal infection is not an indicator of disease.
Unfortunately, no treatment is available to prevent vertical
transmission of CMV infection.
Herpes Simplex
Herpes simplex is a DNA virus fromthe Herpesviridae family, and two different serotypes are known, characterized by
common antigens and specic antigens (HSV1 and HSV2).
Infection with both HSV1 and HSV2 can cause clinical manifestations at the genital or oral level.However, generally,
HSV1 is contracted in childhood and causes orolabial mani-
festations, while HSV2 is typical in adults and causes anogenital lesions. Infection with HSV1 and HSV2 occurs
through direct contact with someone who actively eliminates
the virus. Following the primary infection, after the clinical
phase is over, HSV1 and HSV2 remain latent in the nerve
ganglia for several years of life. However, they can be temporarily reactivated with the appearance of clinical manifestations following various stimuli, such as physical or
emotional stress, menstrual cycle, exposure to UV rays, etc.
Vertical transmission occurs mainly perinatally, during
childbirth, by direct contact of the fetus with maternal secretions; it is more frequent in women with primary infections.
The newborn may present with a localized infection of the
skin, eyes, mouth, or central nervous system (encephalitis) or
a systemic infection involving several organs.
Factors that inuence the probability of vertical transmission are:
• Type of infection: the probability is high (up to 50%) in
mothers with a primary infection contracted towards the
end of gestation, while it is very low in cases where the
primary infection is contracted in the rst trimester of
pregnancy or in cases of recurrent episodes towards the
end of pregnancy.
• Presence of maternal antibodies can cross the placenta
and reach the fetal circulation, thus preventing neonatal
infection.
• Vaginal or cesarean section delivery; the former is associ-
ated with an increased risk of vertical transmission of
infection. Cesarean section is recommended in cases of
primary infection if lesions are present at the time of
delivery or if they appear in the last 6 weeks of
pregnancy.
Screening is based on the serological detection of IgG and
IgM antibodies to HSV1 and 2. Seropositivity for HSV2 is
almost exclusively due to an anogenital infection, while a
positive result for HSV1in an asymptomatic subject may be
due to an orolabial or anogenital infection. In the case of
active lesions, virus isolation by culture is indicated.
However, it could be false positive in the case of recurrent or
healing lesions. Viral DNA detection by PCR cannot always
be performed on genital samples.
Complete Blood Count andHemoglobin
It is crucial to perform a complete blood count as a screening
test to assess the presence of any alterations and intervene
preventively; for example, in the case of a reduction of the
average cell volume and morphological alterations of the
erythrocytes, the hemoglobin balance must be evaluated in
order to identify a possible hemoglobinopathy.
428
https://t.me/medicina_free
M. Ciaccio and L. Agnello
Hemoglobinopathy is a blood disorder due to a genetic defect
in one or more globins constituting the tetramer of hemoglobin (Hb), which can be qualitative (structural defects or Hb
variants) or quantitative (synthesis defects or thalassemias).
If hematological alterations due to hemoglobin defects are
found in the woman, it is important to also evaluate the
hemoglobin status of the partner to estimate the risk that the
fetus could be affected by hemoglobinopathies, which in
homozygosity can be associated with variable levels of
anemia.
The hemoglobin balance, assessed by separative methods
such as high-performance liquid chromatography or capillary electrophoresis, represents a rst-level examination that
provides qualitative and quantitative data regarding all
hemoglobin fractions present in the circulation. In the case
of suspected sickle cell anemia (the presence of the HbS
variant), the sickle cell test represents a useful diagnostic
conrmation tool. As far as the other hemoglobinopathies
are concerned, the blood count resultsand the blood smear
are valid diagnostic aids. However, the characterization of
hemoglobin defects is only possible using second-level
investigations based on molecular tests aimed to identify
mutations in the genes encoding for globin chains.
Glycemia
It is important to evaluate glycemia in the preconceptional
period, especially for a woman with diabetes, in order to
ensure that she is in a state of good glycemic compensation
and, therefore, reduce the risk of miscarriage or fetal
malformations.
Pap Test
The Pap test is a diagnostic test for the prevention of cervical
cancer. Its name comes from the surname of its inventor,
Doctor Georgios Papanicolaou. The test consists of taking
cells from the cervix and the cervical canal, smudged on a
slide, stained according to the Papanicolau method, and
examined under a microscope.
Ascertainment ofPregnancy
Following a delay in the menstrual cycle, when the possibility of pregnancy is suspected, investigations to conrm conception are based on detecting human chorionic gonadotropin
(hCG) in blood or urine.
hCG is a glycoprotein hormone consisting of two subunits, α and β, noncovalently linked; the α subunit is identical to that of pituitary glycoprotein hormones, such as
luteinizing hormone (LH), stimulating follicle hormone
(FSH), and thyroid stimulating hormone (TSH), while the β
subunit is specic for hCG. hCG is produced by trophoblastic tissue and therefore by the placenta during pregnancy, in
trophoblastic pathology, and, to a lesser extent, by some
poorly differentiated neoplasms. Indeed, following conception, hCG begins to be produced as early as the blastocyst,
before implantation occurs.
In serum and urine, hCG may be present in different
forms, such as the biologically active form and molecular
forms that result from the dissociation or degradation of
hCG.In particular, the modied heterodimer can be found as
well as free α and β subunits or degradation products, such as
the β-core fragment. In a physiological pregnancy, generally,
the circulating concentrations of these molecular forms are
low. However, some conditions, such asDown’s syndrome,
trophoblastic pathologies, and some neoplasms (testicle,
ovary, breast, lung, and pancreas), are characterized by an
increase in these forms.
The concentration of the biologically active form of hCG,
both in serum and urine, increases exponentially during the
rst trimester of pregnancy, doubling every 48 h until it
peaks around the 10th week of gestation. From the 10th
week of gestation, the hCG concentration decreases progressively and will no longer be determinable a few weeks after
delivery. The biologically active form of hCG has a half-life
of about 40h. During the rst few weeks of pregnancy, hCG
plays a vital role in maintaining the function of the corpus
luteum. If an ectopic (extra-uterine) pregnancy occurs, hCG
levels in the blood increase at a reduced rate. Therefore, hCG
blood levels should be monitored over time if an ectopic
pregnancy is suspected.
Furthermore, hCG levels can be altered if the fetus has
chromosomal defects like Down’s syndrome. The hCG assay
is part of a screening protocol for detecting fetal chromosomal abnormalities. The minimum increase in hCG value in
48h for an evolving pregnancy is 53%, while the minimum
decrease in case of miscarriage is 21–35%, depending on the
initial value. In 71% of cases of ectopic pregnancy, there is a
lower increase or decrease in hCG for an evolving pregnancy
or a miscarriage, respectively.
The quickest and easiest way to ascertain pregnancy is
to perform a point-of-care test, which can be purchased in
pharmacies or in large-scale retail trade and provides qualitative information with high sensitivity on the presence of
hCG in the urine. To be reliable, the test should not be performed before 15–20days from the date of presumed conception. Generally, point-of-care tests can identify an hCG
concentration ≥25 mIU/mL. At low doses of hCG, the
presence of FSH and LH may generate false positives;
therefore, it is essential to perform two consecutive determinations. Positive tests should, however, be conrmed by
a serum hCG assay.
30 The Role of Laboratory inPregnancy
https://t.me/medicina_free
429
The test is positive in the presence of physiological pregnancy, but also ectopic pregnancy, molar pregnancy (an
unsuccessful pregnancy in which a nonviable fertilized egg
implants in the uterus and results in the establishment of a
pregnancy that will not be carried to term), and choriocarcinoma (a rare neoplasm of the trophoblast that develops inside
the uterus).
The test is negative if the urine is diluted in the case of
fetal death or miscarriage. Point-of-care tests and serum
assays are performed by immunochromatographic methods
using antibodies directed against different epitopes of hCG
or its free subunits.
Pregnancy Laboratory Test
During pregnancy, it is important to carry out periodic laboratory tests, at least every 3 months, in order to evaluate the
evolution of the pregnancy and to identify at an early stage
any pathological alterations associated with the state of pregnancy and potentially dangerous to the health of the mother
and the fetus, such as anemia or gestational diabetes; timely
intervention through the administration of appropriate therapy can prevent complications. It is important to emphasize
that pregnancy is a clinical condition characterized by physiological changes associated with altered levels of some laboratory parameters. It is therefore essential to know the
reference values in pregnancy to correctly interpret the laboratory data.
Laboratory tests that should be performed during pregnancy are listed in Table30.3.
Pregnancy is associated with physiological anemia, characterized by hemoglobin levels lower than the reference values due to hemodilution. From the sixth week of pregnancy,
it is generally observed a rapid and important increase in
plasma volume and, to a lesser extent, an increase in the volume of red blood cells due to the erythroid hyperplasia that
characterizes pregnancy (the bone marrow meets theoxygen
demand that increases progressively with the production of
red blood cells). These physiological changes lead to a dilution of the blood, resulting in a reduction in hematocrit levels, red blood cells, and hemoglobin. The fall in hemoglobin
concentration reduces blood viscosity, thus improving placental perfusion and facilitating the maternal–fetal exchange
of oxygen and nutrients.
A slightly increased plasma volume with an increased
hemoglobin concentration increases blood viscosity, reducing blood ow to tissues (possible preeclampsia). In pregnancy, a hemoglobin value ≥11g/dL is considered normal;
hemoglobin values <11g/dL should raise the suspicion of
pathological anemia and, therefore, require further investigation. Ferritin is the most sensitive and specic biomarker to
assess the extent of iron stores and establish the sideropenic
Table 30.3 Tests to be performed during pregnancy
First trimester of pregnancy (within the 13th week of gestation)
Complete blood count with platelet count
TORCH agents (generally, the search for specic antibodies to
toxoplasma, rubella, HIV, and syphilis are required)
Glycemia and glycated hemoglobin to identify the presence of
overt diabetes
Chemical-physical and microscopic examination of the urine
Hepatic and renal function indices: transaminases and
creatininemia
Indirect Coomb’s test. If already performed in the preconception
phase, repeat in case of Rh-negative women at risk of
immunization
Second trimester of pregnancy (14th to 27th week of gestation)
Complete blood count
Complete urinalysis
Urine culture, in case of signicant bacteriuria: at least 100,000
colonies per mL of urine
OGTT
Test for Rubella and toxoplasmosis, in case of seronegative
women
Third trimester of pregnancy (since the 28th week of gestation to
the pregnancy end)
Complete blood count
Complete urinalysis
Urine culture, in case of signicant bacteriuria: at least 100,000
colonies per mL of urine
Test for Rubella and toxoplasmosis, in case of seronegative
women
Ferritin, in case of reduction of the average globular volume
Hepatitis B virus antigen (HbsAg)
Antibodies to HCV and HIV, in case of risk assessed based on the
history
OGTT oral glucose tolerance test, HCV hepatitis C virus, HIV human
immunodeciency virus
nature of anemia. Hemoglobin values <8.5g/dL are associated with an increased risk of poor neonatal outcomes.
Plasma transferrin increases by 1.5–2 fold. In the last trimester of pregnancy, 90% of plasma iron is released via transferrin to receptors located on the membrane of
syncytiotrophoblast cells, which are the same as those found
on the membranes of reticulocytes. Therefore, ferritin
decreases during pregnancy, partly due to hemodilution and
partly due to the depletion of iron resources.
At the end of the third trimester of pregnancy, mild thrombocytopenia (with platelet counts not less than 100,000/mL)
can be observed, which is generally a benign, asymptomatic
condition that tends to resolve within 2 months of delivery.
There may also be a slight increase in white blood cells, predominantly neutrophils, due to the action of estrogen. In general, pregnancy is characterized by a state of physiological
hypercoagulability to ensure the deposition of brin between
the uterine wall and the chorionic villi and maintain placental integrity; it is observed, therefore, an increase in brinogen, factors V, VII, VIII, IX, and X, while decreasing
brinolytic activity, free protein S, and antithrombin III.This
condition determines an increased thrombotic risk from 4 to
10 times throughout the pregnancy that remains until
430
https://t.me/medicina_free
M. Ciaccio and L. Agnello
2–3weeks after delivery. In addition to the proteins involved
in the hemostatic process, pregnancy is characterized by
alterations in the serum concentration of other proteins produced in the liver. In particular, there is an increase in alkaline phosphatase, in part due to the placental production of
one of its isoenzymes, a reduction in gammaglutamylpeptidase, and serum albumin. Additionally, total proteins and the
albumin/globulin ratio are signicantly reduced, while
aspartate aminotransferase and alanine transaminase remain
unchanged.
Pregnancy also induces adaptations in renal function to
allow the gain of Na+and water to ensure the expansion of
extracellular volume and the growth of the fetus. During
pregnancy, glomerular plasma ow increases progressively,
reaching a maximum peak around the 20th week of gestation
(up to 50% more) and remaining at this level throughout the
pregnancy. In parallel, the glomerular ltration rate increases.
Under these conditions, there is an increase in glucose excretion (sometimes glycosuria can be observed), creatinine,
urea, proteins, and uric acid in the rst trimester. Circulating
glucose, creatinine, urea, and protein tend to decrease during
pregnancy; uric acid is low in the rst trimester, increases in
the second, and is higher than normal in the third trimester.
This occurs because tubular reabsorption changes normalize
a few weeks after delivery.
The urine test allows to detect bacterial infections of the
urinary tract, which are quite common in pregnancy, or other
changes that may pose a risk to the fetus and the mother.
The presence of bacteria can be associated with the typical symptoms of cystitis (burning during urination and frequent urination) or be asymptomatic. Early detection of
bacteriuria is important because it is associated with an
increased risk of pyelonephritis due to the increased uterus
volume, which compresses the bladder and urinary tract and
causes stagnation of urine. In this condition, bacteria in the
urine are more likely to travel up to the kidneys and cause the
infection. In addition, untreated bacteriuria is associated
with an increased risk of low birth weight and preterm birth
due to premature rupture of membranes. Urinary tract infections in pregnancy could also trigger situations that lead to
gestational hypertension or preeclampsia. The bacterium
responsible for most infections is Escherichia coli.
The test is performed on a urine sample collected in the
morning (intermediate micturition). The presence of nitrites,
signicant bacteriuria (>100,000 colonies per mL of urine),
and increased leukocytes should raise the suspicion of urinary tract infection; to conrm the suspicion, a urinalysis
with an antibiogram should be performed to isolate the specic pathogenic microorganism, determine antibiotic sensitivity, and direct the choice of therapy. The test is positive for
a growth rate of ≥105 colony-forming units/mL.A urine cul-
ture is also performed in the presence of typical symptoms
commonly referred to as cystitis.
Squamous epithelial cells derived from the vaginal epithelium can be found in urine. If present in low concentrations and in the absence of other altered parameters, the data
is irrelevant, but if present in high concentrations and associated with bacteriuria and blood counts, it could indicate the
presence of vaginitis. In this case, a vaginal swab should be
performed to conrm the presence of an infection and proceed with antibiotic therapy.
Erythrocytes should not be detectable in urine. However,
their presence in the urine sediment could indicate cystitis, a
cervical polyp, a vaginal fold, or inammation of the lower
urinary tract; it could also be due to recent intense sexual
activity.
Glycosuria should not be present. However, small
amounts of glucose in the urine may be found in pregnancy
due to physiological changes in the kidney; high concentrations may indicate gestational diabetes.
Protein should generally not be detectable in the urine,
although a certain amount of protein is physiologically lost
through the urine. Detecting proteinuria before the 20th
week of gestation may indicate a renal alteration, while a
later nding may indicate preeclampsia or gestosis.
Gestational Diabetes
Gestational diabetes mellitus (GDM) is classically dened as
a condition of impaired glucose tolerance of variable degree
and severity that occurs during pregnancy (usually in the second or third trimester) and generally regresses after delivery.
However, it can recur at a distance, preferentially with the
characteristics of type 2 diabetes.
GDM is the most common metabolic alteration in pregnancy that, if not correctly recognized and adequately
treated, is associated with high maternal–fetal morbidity,
mainly related to excessive fetal growth (macrosomia).
Numerous studies have shown that early treatment of GDM
reduces the incidence of adverse pregnancy outcomes.
GDM is, from a biochemical point of view, characterized
by reduced insulin secretion accompanied by increased
peripheral insulin resistance, two conditions typical of type 2
diabetes mellitus. In GDM, reduced insulin secretion cannot
compensate for the insulin resistance characteristic of pregnancy. Indeed, as already mentioned, during pregnancy, the
organism undergoes a physiological adaptation characterized by endocrine-metabolic alterations necessary to guarantee the supply of nutrients to the fetus and adequately prepare
the maternal organism for childbirth and lactation
(Table30.4). These alterations are due to the action of hor-
30 The Role of Laboratory inPregnancy
https://t.me/medicina_free
431
Table 30.4 Metabolic changes in pregnancy
Glucose metabolism
Reduction of insulin sensitivity
Increased β-cell response
Modest increase in postprandial blood glucose
Lipid metabolism
Alteration of circulating levels of free fatty acids, triglycerides,
cholesterol, phospholipids (initial reduction in the rst 8 weeks
followed by an increase)
Ketone bodiessynthesis
Protein metabolism
Reduction of circulating amino acid levels in fasting and in the
postprandial state
mones produced during pregnancy, such as estrogen, progesterone, cortisol, and placental lactogenic hormone.
The condition of insulin resistance that sets in with the
progress of pregnancy, more evident in muscle and adipose
tissue, is a physiological condition aimed at fetal growth.
The reduced insulin-mediated utilization of glucose by the
maternal organism determines, indeed, greater utilization
of lipid substrates for energy purposes and, at the same
time, guarantees the fetus a greater intake of carbohydrates.
In addition, moderate but more prolonged postprandial
hyperglycemia, which develops due to lower insulin sensitivity, favors the ow of nutrients from the mother to the
fetus.
In GDM, the reduced action of insulin leads to an excess
of nutrients in the circulation, such as glucose, lipids, and
amino acids, which, crossing the placenta, cause hyperinsulinism in the fetus that, in turn, leads to organomegaly and
macrosomia.
It is important to distinguish between overt diabetes in
pregnancy and gestational diabetes. Manifest diabetes means
the presence of diabetes that existed before pregnancy and
was not recognized up to that moment; gestational diabetes
means, instead, a form of diabetes that arose during pregnancy. The laboratory tests for diagnosing diabetes in pregnancy, both manifest diabetes and GDM, are fasting blood
glucose, glycated hemoglobin, and the OGTT (oral glucose
tolerance test). In particular, after pregnancy assessment, all
women should bescreened for overt diabetes by evaluating
glycemia (fasting and random) and glycated hemoglobin
within the rst trimester of pregnancy. For the diagnosis of
overt diabetes, the same criteria used in the general population are used:
• Fasting blood glucose ≥126mg/dL (to be conrmed by a
second blood test)
• Random blood glucose ≥200mg/dL (to be conrmed by
fasting blood glucose ≥126mg/dL)
Table 30.5
Risk factors (OGTT at 24–28weeks)
Family history of type 2 diabetes in rst-degree relatives
Previous gestational diabetes
Fetal macrosomia in previous pregnancies
Overweight and obesity (BMI ≥25kg/m2)
Age≥35years
High-risk ethnic groups (South Asia, Middle East, Caribbean)
High risk factors (OGTT at 16–18weeks)
Obesity (BMI ≥30kg/m2)
Previous gestational diabetes
Fasting blood glucose 100–125mg/dL, in early pregnancy or in
BMI body mass index, OGTT oral glucose tolerance test
Risk factors for gestational diabetes mellitus
the past
• HbA1c≥48 mmol/mol (≥ 6.5%) (to be conrmed in a
second sample)
Women diagnosed with overt diabetes should undergo
intensive metabolic monitoring, as recommended for gestational diabetes.
Screening for GDM is based, rst of all, on the assess-
ment of specic risk factors (Table30.5); women who present at least one risk factor for GDM should perform an
OGTT with 75g ofglucose between the 24th and 28th weeks
of pregnancy because GDM usually occurs in the second
half of pregnancy. However, women with high riskfactors
should be screened early by performing a 75-g glucose
OGTT between 16 and 18weeks of pregnancy, to be repeated
between 24 and 28weeks if negative. Figure30.1 shows the
diagnostic procedure for screening and diagnosing diabetes
in pregnancy.
Women with previous GDM should be screened for dia-
betes mellitus 2 by performing an OGTT with 75g of glucose 6weeks after delivery and within 6months. If the test is
negative, the OGTT should be repeated every 3 years; if
impaired glucose tolerance (IFG or IGT) is found, the test
should be repeatedyearly.
The OGTT should be performed on an empty stomach in
the morning by administering a solution consisting of 75g of
glucose dissolved in 300mL of water. There are no particular
indications to follow in the days preceding the test, but consuming at least 150 g of carbohydrates per day is recommended. During the test, assuming the sitting position and
refrain from eating, drinking, and smoking is necessary.
Blood sampling to obtain the plasma on which the glycemia
will be performed by the enzymatic method will be done
before the administration of the glucose solution (basal glycemia) and after 1 and 2 h from the administration of the
solution. Table30.6 shows the glycemia values that allow the
diagnosis of gestational diabetes.
432
https://t.me/medicina_free
M. Ciaccio and L. Agnello
First visit during pregnancy
Screening for
overt diabetes
• Fasting blood glucose ≥ 126 mg/dL
• Random blood glucose ≥ 200 mg/dL
• HbA1c ≥ 48 mmol/mol (≥ 6.5%)
Overt
Diabetes
Fig. 30.1 Gestational diabetes diagnostic algorithm. (Copyright EDISES 2021. Reproduced with permission)
• First-degree family history of type 2 diabetes
• Previous gestational diabetes
• Previous macrosomia
• Overweight and obesity (BMI ≥ 25 kg/m
• Age ≥ 35 years
• High-risk ethnicities
OGTT 75 g at 24–28 weeks
Positive
Gestational
diabetes mellitus
Screening for
gestational diabetes
Risk factor assessment
2
)
• Obesity (BMI ≥ 30 kg/m2)
• Previous gestational diabetes
• Fasting blood glucose 100–125 mg/dL
OGTT 75 g at 16–18 weeks
NegativePositive
Table 30.6 Diagnostic criteria for gestational diabetes mellitus
Times Glycemia (mg/dL)
0min
1h
2h
≥92
≥180
≥153
Preeclampsia andEclampsia
Preeclampsia is a clinical condition associated with hypertension and proteinuria, with or without edema, that occurs
in the second half of pregnancy, no earlier than the 20th week
of gestation, in previously normotensive, non-proteinuric
women and usually disappears after delivery, within
6–12 weeks. Hypertension is a systolic blood pressure
≥140mmHg or diastolic blood pressure ≥90mmHg in two
successive measurements at least 4hours apart. Proteinuria
is dened as an excretion ≥300mg/24h or a urinary protein/
creatinine ratio ≥0.3mg/mg (30mg/mmol) on the extemporaneous sample, or, if quantitative measurement is not available, a dipstick nding of ≥1+ proteinuria. Preeclampsia can
also be dened by the concomitant nding of hypertension
without proteinuria if thrombocytopenia, increased serum
creatinine, transaminases, pulmonary edema, and neurological symptoms such as headache and/or visual disturbances
are present (Table30.7).
Table 30.7
Hypertension: Systolic blood pressure ≥140mmHg or diastolic
blood pressure ≥90mmHg on two occasions at least 4h apart after
the 20th week of gestation in a previously normotensive woman
And
Proteinuria ≥300mg/24h or a urinary protein/creatinine ratio
≥0.3mg/mg (30mg/mmol) on the impromptu sample or, if
quantitative measurement is not available, test strip detection
(dipstick) of proteinuria ≥1+
Or
Hypertension: Systolic blood pressure ≥140mmHg or diastolic
blood pressure ≥90mmHg on two occasions at least 4h apart after
the 20th week of gestation in a previously normotensive woman
along with one or more of the following conditions (with or without
proteinuria):
-Platelet count <100,000 plt/microL
- Serum creatinine >1.1mg/dL or at least 50% increase in serum
-Transaminases ≥2 times the upper reference limit
-Pulmonary edema
-Neurological symptoms such as headache or visual disturbances
Diagnostic criteria of preeclampsia
creatinine in the absence of known kidney disease
A recent meta-analysis estimated that approximately
4.6% of pregnancies worldwide are complicated by pre-
eclampsia. Preeclampsia is dened as severe if the signs and/
or symptoms listed in Table30.8 are present.
Preeclampsia can have signicant maternal–fetal conse-
quences such as placental abruption, preterm delivery, low
30 The Role of Laboratory inPregnancy
https://t.me/medicina_free
433
Table 30.8 Conditions associated with severe preeclampsia
Neurological symptoms
Appearance of visual disturbances (scotoma, cortical blindness, and
retinal vasospasm), severe headache or resistant to pain relief, altered
mental status.
Liver disorders
Severe and persistent pain in the right upper abdominal or epigastric
quadrant not justied by another diagnosis or nding of
transaminases ≥2 times the upper limit of reference or both
conditions.
Severe arterial hypertension
Systolic blood pressure ≥160mmHg or diastolic blood pressure
≥110mmHg on at least two occasions
Thrombocytopenia
Platelets <100.000 plt/microL
Kidney alterations
Serum creatinine >1.1mg/dL or at least 50% increase in serum
creatinine withoutknown renal disease.
Pulmonary edema
birth weight, and fetal death; the most severe complication of
preeclampsia is eclampsia, or gestosis, characterized by convulsive seizures and/or maternal coma. Preeclampsia is the
result of an altered function of the placenta, the etiology of
which is not yet fully known but could be linked to various
factors such as poor development of the uterine placental spiral arterioles (which reduces uteroplacental blood ow in
late pregnancy), immunological alterations, and placental
ischemia or infarction. Preeclampsia may also be asymptomatic or cause edema associated with excessive weight gain.
Identifying risk factors for preeclampsia is essential to initiating appropriate prophylaxis by week 20.
The main risk factors for preeclampsia are:
• Preeclampsia in previous pregnancies, especially those
with adverse outcomes
• Pre-existing chronic hypertension
• Diabetes
• Multiple pregnancies
• Chronic kidney disease
• Autoimmune diseases (antiphospholipid antibody syndrome, systemic lupus erythematosus)
Moderate risk factors include nulliparity, obesity, mater-
nal age <20 or >35 years, family history of preeclampsia,
thrombophilia, or other thrombotic conditions. Right from
the beginning of pregnancy, it is advisable to carefully assess
the individual risk conferred by clinical and anamnestic factors and, if necessary, to start the pregnant woman with more
stringent surveillance or pharmacological prophylaxis.
The monitoring of women at risk of preeclampsia includes
the assessment of blood pressure, platelet count, serum creatinine, liver function indexes, and proteinuria within 24h.
These evaluations should be carried out from the beginning
of pregnancy and help in more advanced gestational periods
to identify new onset preeclampsia concerning preexisting
pathological conditions.
Given the clinical relevance of preeclampsia for its complications on mother and fetus and the absence of adequate
diagnostic screening tools, in recent years has been conducted an intense research activity aimed at identifying
potential biomarkers predictive of preeclampsia.
Studies on the pathogenesis of preeclampsia have highlighted the importance of an aberrant synthesis of angiogenesis modulators in determining the endothelial damage and
increased capillary permeability that underlie the pathogenesis. Angiogenetic factors of signicant interest in this area
include vascular endothelial growth factor (VEGF) and placental growth factor, along with some proteins with known
anti-angiogenic activity such as Soluble Endoglin (sEng),
the truncated form of the receptor for VEGF (Flt-1), known
as soluble FMS-like Tyrosine Kinase-1 (sFlt-1). In the ischemic trophoblast, a characteristic feature of eclampsia, the
production of anti-angiogenic factors (sEng and sFlt-1)
increases, and that of angiogenic factors (VEGF, PIGF) is
reduced. Alterations in the levels of these factors in the
mother’s plasma or urine precede the onset of preeclampsia
by a few weeks, correlate with the severity of the disease,
and normalize after delivery. These tests seem to be useful,
especially in more advanced gestational periods, while they
seem to be of little help before the 20th week. In particular, a
recent meta-analysis has shown that the sFlt-1/PIGF ratio
has the best diagnostic performance in predicting preeclampsia if used in the second-third trimester of pregnancy (after
20 weeks), with a sensitivity of 80% and a specicity of
92%. Growing scientic evidence has shown that increases
in circulating proteins, such as pregnancy-associated plasma
protein-A (PAPP-A), or changes in circulating free DNA in
the rst and second trimester predict adverse outcomes,
including preeclampsia. However, this association is not
strong enough to justify routine clinical use of these tests
and, more importantly, to modify the clinical care pathway
of women at risk for preeclampsia.
Women at high risk of developing preeclampsia (previous
preeclampsia, prepregnancy diabetes, prepregnancy hypertension, and renal disease) should receive low-dose aspirin
prophylaxis. Most risk factors are not modiable, so interventions to reduce the likelihood of preeclampsia are limited
to pharmacological prophylaxis and weight gain during
pregnancy.
Prophylaxis aims to prevent severe and potentially fatal
complications; uncomplicated preeclampsia is reversible and
begins to resolve spontaneously after childbirth.
In the absence of maternal and/or fetal complications
requiring immediate termination of pregnancy, the most
important factor in the treatment decision is the gestational
age. The safest treatment for the mother is delivery, but it
may not be safe for the fetus, depending on the gestational
434
https://t.me/medicina_free
M. Ciaccio and L. Agnello
age. In early gestational periods, conservative treatment aims
to achieve fetal maturity (especially respiratory maturity)
while keeping the maternal clinical condition under constant
and careful control.
Pharmacological control of hypertension allows to avoid
maternal complications directly related to blood pressure
values, such as placental abruption, heart failure, and maternal cerebral hemorrhage. However, itcannot modify the disease’s progression.
Eclampsia, or gestosis, consists of generalized tonic–
clonic seizures in women with preeclampsia. It represents
the convulsive manifestation of preeclampsia and is considered one of its most severe clinical manifestations.
Eclampsia most frequently occurs before delivery (almost
always after the 28th week) but can also occur afterward
(after 48h and up to 4weeks) or during labor. In the hours
preceding the onset of convulsions, the woman may present
signs and symptoms such as hypertension, headache, visual
disturbances, and epigastric pain; in 25–40% of cases, there
are no prodromal signs.
Eclampsia occurs in 2–3% of women with severe preeclampsia who do not receive prophylaxis and up to 0.6% of
women with non-severe preeclampsia. In industrialized
countries, it has an incidence ranging from 1.5 to 10
cases/10,000 deliveries. It is difcult to predict the eclampsiaonset; the only way to reduce its incidence is to administer prophylaxis with magnesium sulfate in cases at risk, that
is, in cases of severe preeclampsia, and especially when a
headache, visual disturbances, and epigastric pain are present. Prophylaxis is not recommended in all other cases (moderate or mild preeclampsia). The diagnosis of eclampsia is
essentially clinical and is based on the above-mentioned neurological symptoms. If the neurological decit is not persistent, investigations are limited to those for screening for
preeclampsia. Vice versa, it is appropriate to consider a differential diagnosis aimed at excluding other causes incidental to pregnancy (brain tumors, brain aneurysms) or
conditions exacerbated by the gravid state (thrombotic
thrombocytopenic purpura, hemolytic-uremic syndrome,
cerebral venous thrombosis).
The therapeutic approach is based on maintaining maternal oxygenation and protection from accidental trauma during the acute crisis and treating hypertension and seizures
with magnesium sulfate. Delivery is the only curative
treatment.
Once eclampsia has been established, it is helpful to
maintain intensive monitoring for 24–48h after the convulsive crisis has ceased. Concerning the clinical condition, it is
necessary to frequently monitor hemoglobinemia, hematocrit and platelets, liver function indexes (transaminases, lactate dehydrogenase, and bilirubin), and renal function
indexes (creatininemia and serum electrolytes). Coagulation
investigations are indicated in the case of hemolysis elevated
liver enzymes, low platelet syndrome or disseminated intravascular coagulation.
Prenatal Screening forDown Syndrome
Down syndrome is, in about 95% of cases, the result of nondisjunction of chromosome 21in oogenesis or spermatogenesis (trisomy 21). The gold standard laboratory test to
diagnose a fetus with Down syndrome is karyotype analysis
by chorionic villus sampling or amniocentesis. The latter are
invasive techniques associated with a low risk of fetal loss. A
non-invasive alternative, and therefore not associated with
any risk to the fetus, is the application of tests that estimate
risk by combining information from ultrasound examination
and/or biochemical examination of maternal blood with
maternal age and gestational age. These tests provide the
result in a number; if this value exceeds a specic cut-off, the
test will be positive, and the woman may undergo more invasive investigations, such as amniocentesis and villocentesis.
In particular, ultrasonography evaluates nuchal translucency,
which is the measurement of the thickness of the subcutaneous tissue at the nape of the neck of the fetus, that is, the
space between the skin and the spine. The greater the thickness of nuchal translucency, the greater the probability that
the fetus has Down’s syndrome. Biochemical examinations,
on the other hand, are based on the evaluation of serum
markers such as human chorionic gonadotropin (total or free
beta fraction, hCG), pregnancy-associated plasma protein A
(PAPP-A), alpha-fetoprotein (AFP), unconjugated estriol
(uE3), and inhibin A.Table30.9 shows the main tests available for assessing the risk of Down syndrome. It is important
to note that a positive result from these tests does not indicate
that the fetus will have Down syndrome.
PAPP-A is a glycoprotein of placental origin, produced
mainly in the syncytiotrophoblast.
AFP is a glycoprotein secreted rst by the yolk sac and
then by the fetus’s liverIt has the same functions as albumin;
immediately after birth, its concentrations progressively
decrease until it is absent. AFP can cross the placenta and
reach the maternal circulation, where its levels will be
directly proportional to those in the fetal circulation.
Estriol is a steroid hormone produced in unconjugated
form exclusively during pregnancy by the placenta and fetal
organs: the fetal adrenal glands produce dehydroepiandrosterone sulfate (DHEA-S), which is hydroxylated by the fetal
liver to 16-hydroxy-DHEA-S and subsequently metabolized
by the placenta to form unconjugated estriol. The uE3
secreted by the placenta then passes into the maternal circulation; after conjugation in the liver, it is subsequently eliminated in the urine. The levels of uE3 increase in the maternal
Соседние файлы в папке Библиотека им академика М.И. Перельмана