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OB Pathology > Chapter 55 - The Placenta > Flashcards

Chapter 55 - The Placenta Flashcards

1
Q

Major role of the Placenta

A

To permit the exchange of oxygenated maternal blood (rich in oxygen and nutrients) with deoxygenated fetal blood.

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2
Q

What circulates blood into the placenta?

A

Maternal vessels–coursing posterior to the placenta

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3
Q

Blood from the fetus returns to the placenta through what?

A

The unbilical cord

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4
Q

What 4 things make up the embryonic or fetal membranes?

A

1-Chorion

2-Amnion

3-Yolk Sac

4-Allantois

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5
Q

Implantaion of the blastocyst occurs

A

6-7 days after fertilization

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6
Q

Enlargement of the trophoblasts helps to anchor the blastocyst to the

A

Endometrial lining, or decidua.

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7
Q

2 components of the placenta

A

1-Maternal portion-decidual BASALIS (formed by the endometriial surface)

2-Fetal portion (developed from the chorion frondosum)

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8
Q

Decidual reaction that occurs between the blastocyst and the myometrium

A

Decidua Basalis

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9
Q

decidual reaction occuring over the blastocyst closest to the endometrial cavity

A

Decidua capsularis

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10
Q

A reaction changes in the endometrium opposite the site of implantaion

A

Decidua vera (parietalis)

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11
Q

The fetal trophoblastic tissue that together with the decidua, forms the area for maternal and fetal circulation

A

Chorion Frondosum

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12
Q

The chorion around the gestational sac on the opposite side of impantation

A

Chorion laeve

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13
Q

The fetal surface of the placenta

A

Chorion Plate

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14
Q

The maternal surface of the placenta

A

Basal plate

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15
Q

The major functioning unit of the placenta

A

Chorionic Villus

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16
Q

The maternal blood enters

A

The intervillous spaces

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17
Q

The decisua capsularis is stretched as

A

the embryo and membranes grow

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18
Q

The chorinonic villi opposite the implantation site of the chorionic sac gradually

A

Atrophy and disappear (smooth chorion or chorion laeve)

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19
Q

The maternal surface of the placenta, which lies continuous with the decidua basalis

A

The basal plate

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20
Q

The fetal surface, which is continuous with the surrounding chorion

A

The chorionic plate

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21
Q

Before birth, the fetal membranes and placenta perform the following 4 functions and activities

A

1-Protection

2-Nutrition

3-Respiration

4-Excretion

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22
Q

The fetal membranes and placenta sepatate and are expelled

A

at birth or parturition

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23
Q

Oxygen rich blood passes through the umbilical vein into the ________ through the _________ into the _____ to the______across the _______ into the ________, blood then passes into the _______ and out the ________ to supply the _____ and _______.

A

fetal abdomen

ductus venosus

IVC

RT Atrium

Foramen Ovale

Lt Atrium

Lt Ventricle

Ascending AO

Brain

Upper body

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24
Q

Un-oxygenated blood from the SVC passes into the _____ through the ______ and across the ________, most blood passes through the _______ and into the _______ to the ________, the _______ to the _______ to return to the ______ for respiratory and nutrients exchange.

A

Rt Atrium

RT Ventricle

Main Pulmonary Artery

Ductus Arteriosus

AO Arch

Descending AO

Internal Iliac Arteries

Unbilical Arteries

Placenta

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25
Q

What is dedicated to the survival of the fetus

A

The Placenta

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26
Q

What happens when the fetus is exposed to a poor maternal environment

A

The placenta can often compensate by becoming more efficient

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27
Q

If the fetus is exposed to poor maternal environment that is severe enough, the stresses can lead to

A

placental damage

fetal damage

intrauterine demise and pregnancy loss

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28
Q

3 conditions that decrease uterine blood flow and may reduce maternal placental circulation

A

1-severe hypertension

2-renal disease

3-placental unfarction

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29
Q

Placental defects can cause

A

IUGR

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30
Q

The normal attachment of the cord is usually

A

Near the center of the placenta

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31
Q

insertion of the umbilical cord at the margin of the placenta, within 10mm of the edge

A

Battledore Placenta

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32
Q

A membranous insertin and is best demonstrated with color doppler.

If the membranes cross the internal os it is known as.

A

Velamentous Placenta

Vasa Previa

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33
Q

Normally the placenta will implant on the

A

Anterior, fundal or posterior wall of the uterus

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34
Q

Occasionally the placenta will implant low in the uterus resulting in a condition called

A

Placenta Previa

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35
Q

The Chorion originates from the

A

Trophoblastic cells

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36
Q

The Amnion develops at the

A

28th menstrual day

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37
Q

The amnion fuses with the chorion and can no longer be seen on ultrasound as two separate membranes by

A

16 weeks

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38
Q

The functional endocrine units of the placenta

A

Chorionic villi

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39
Q

A central core of the placenta is surrounded by an _________ and an__________

A

Inner layer (cytotrophoblast)

Outer layer (syncytiotrophoblast)

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40
Q

The inner layer (cytotrophobast) of the placenta produces

A

Neuropeptides

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41
Q

The outer layer (syncytiotrophoblast) of the placenta produces

A

The protien hCG

human placenta lactogen (hPL)

the sex steroids, estrogen and progesterone

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42
Q

The function of hCG

A

to maintain the corpus luteum in early pregnancy

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43
Q

hPL is responsible for

A

The promotion of lyplysis and an antiinsulin action that serves to direct nutirents to the fetus

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44
Q

Progesterone production is

A

exclusively a maternal-placental interaction, with no contibution from the fetus

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45
Q

The placenta is identified on sonography as early as

A

8 menstrual weeks

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46
Q

The substance of the placenta assumes a relatively __________ pebble-gray appeaarance between______ and is easily recognized with its characteristically _______ borders

A

Homogeneous

8-20 weeks

Smooth

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47
Q

The fetal surface of the placenta (portion closest to the fetus) is represented by the

A

Echogenic chorionic plate

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48
Q

The second surface which lies at the junction of the myometrim

A

Basal plate

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49
Q

Maternal bloos vessels from the endometrium run behind the basal plate and are often confused with

A

Placental abruption

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50
Q

The thickness of the placenta varies with gestational age with a diameter of

A

Less than 2-3cm in fetuses greater than 23 weeks.

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51
Q

The size of the placenta corresponds to the

A

Gestaional age. And rarely exceeds 4cm

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52
Q

When evaluating the thickness you should maintain a

A

Perpendicular measurment of the placental surface in relation to the myometrial wall

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53
Q

Enlarged placentas may also be associated with

A

Rh sensitization

Diabetes of pregnancy

congenital anomalies

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54
Q

Cystic structures representing large fetal vessels are commonly observed coursing

A

Behind the chorionic plate and between the amnion and chorion layers

(Several sonolucent areas within the placenta may confuse you while unfamiliar with the wide range of placental variants)

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55
Q

Sonographic evaluation of the normal placenta

A

A- amniotic fluid

f- fetus

P- placenta

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56
Q
A

Real time observation of blood flow or color Doppler helps to differentiate these vessels

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57
Q

______ may also be found in th eintervillous spave posterior to the chorionic plate (subchorionic)

A

Deposits of fibrin

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58
Q

May also be seen within the placental substance

A

Placental sonolucencies.

(These have been refered to as placental lakes and are most often a normal finding)

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59
Q

The placenta is separated from the myometrium by

A

A subplacental venous complex

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60
Q
A

Transverse image of the placenta as it lies along the anterior uterine wall. Sonolucencies are seen representing placental lakes (arrows).

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61
Q

A thin hypoechoic layer posterior to the basilar vein

A

The myometrium

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62
Q

These veins can become very prominent and should not be confused for a retroplacental or marginal hemorrhage

A

Basial and marginal

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63
Q

To evaluate the position and size of the placenta you should scan

A

longitudinally from side to side and transversely from inferior to superior

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64
Q

While scanning the placenta what should be documented

A

the insertion of the cord and inferior edge of the placenta

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65
Q

The placenta may be seen along the

A

fundus, anterior or lateral uterine wall

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66
Q

The location of the placenta can change framatically with

A

an over distended urinary bladder or focal uterine contractions.

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67
Q

________ should not be confused for aplacental pathology, The appearance of these contractions may distort the uterine contour and the suspicious area may be rescanned after 15-20 minutes to see if the uterine contour has returned to normal.

A

Braxton Hicks contractions

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68
Q

The position of the placenta should be described with

A

Specific na,es given to it by it’s point of origin.

Fundal/Anterior

Fundal.Posterior

Left Lateral, etc….

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69
Q

To visualize the internal os of the cervix and see the relationship of the placenta to the internal os

A

A sagittal image of the lower uterine segment (LUS) and cervix should be obtained

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70
Q

A normally implanted placenta may appear to cover the internal os if

A

The maternal bladder is over filled.

(Emptying the bladder reduces the pressure on the lower uterine segment and allows the cervix to assume a more normal position but makes it difficult to see the cervix)

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71
Q

Diagnosis of a posterior previa may be dificult because the fetal skull bones block transmission if the

A

Fetal head is low in the pelvis.

(You may try tilting the patient in a slight Trendelenburg’s position or using the endovaginal or transperineal approach to relieve pressure of the uterus on the lowe uterine segment-LUS-)

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72
Q

Especially when evaluating the inferior edge of the placenta the best imaging tool to identify the lower uterine segment is

A

Transvaginal sonography

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73
Q
A

LUS-lower uterine segment

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74
Q

A previa noted on a scan alerts the obstetrician the

A

no pelvic exam should be performed.

(A finger inadvertently pushed through an unknown previa can cause bleeding)

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75
Q

A placenta noted to be low-lying early in pregnancy can be followed with

A

consecutice scans to see whether it persists

76
Q

When the placenta appears to lie on both anterior and posterior uterine walls, check for

A

A laterally positioned placenta

77
Q

When the placenta doesn’t appear to connunicate a

A

Succenturiate placenta should be considered

78
Q

This is a condition in which there are additional placental lobes jointed to the main placenta by blood vessels

A

Succenturiate plcenta

79
Q

A, Placenta (P) appears to be located on both anterior and posterior uterine walls. c, Umbilical cord.

A

B, By scanning laterally, the placenta is seen to communicate (arrow), representing a lateral placenta rather than a succenturiate lobed placenta

80
Q

A clinician should be notified of the condition, Succenturiate placenta because

A

There is a risk that these connecting blod vessels may rupture or that an extra lobe may be inadvertently left in the uterus after delivery

81
Q

The concept that the placenta changes its position within the uterine cavity has been termed __________,implying that the placenta actually moves and relocates

A

Placental migration.

(It may be that the placenta actually does not move, but the position appears changed because of the physiologic enlargement of the uterus and development of the lower uterine segment)

82
Q

A placenta previa should not be diagnosed before

A

20 weeks

83
Q

If the placenta is a complete previa in the _______________ it is unlikely to change it’s position drastically

A

Early 2nd trimester

84
Q

If the placenta is a complete previa in the _______________ it will most likely remain a complete previa

A

3rd trimester

85
Q

PLacental function can be assessed by

A

Color, power and pulsed doppler

86
Q

The Uterine artery should a ________ flow pattern in the 1st trimester, and should become a _________ flow pattern in the 2nd trimester

A

High-resistance

Low-resistance

87
Q

In the 1st trimester, the flow velocity waveform shows a notched appearance in diastole; this notch usually disappears by

A

24 weeks

88
Q

In the 2nd trimester, the doppler signals of the ________ are variable depending on the location of the placenta with the lowest reistance on the __________

A

Uterin Arteries

Placental side

89
Q

4 Normal characteristics of a normal placenta at delivery

A

1- measures about 15-20cm in diameter

2-Discoid in shape

3- Weighs about 600g

4- Measures less than 4cm in thickness

90
Q

The placenta should be evaluated to have been delivered intact to prevent complications of

A

postpartum hemorrhage or infection

91
Q

Membranes of the amnion and chorion are inspected for

A

Color and consistency, with attention to meconium staining or signs of infection

92
Q

Short umbilical cords, less than 30cm, may result in

A

Traction during labor and delivery, leading to tearing of the cord, abruption or inversion of the uterus

93
Q

Long umilical cords are more likely to

A

Prolapse, become twisted around teh fetus, or tie in true knots

94
Q

A protein found throughout the placenta but is most pronounced in the floor of the placenta and increases continuously throughout pregnancy.

A

Fibrin. Wich is derived from fibrinogen

95
Q

On ultrasound, this fibrin deposition appears as hypoechoic area beneath the

A

chorionic plate of the placenta

96
Q

Differential consideration of fibrin deposition (subchorionic) includes

A

A venous lake or a subchorionic hematoma

97
Q

The mayjor pathologic processes seen in the placenta that can adversely effect pregnancy outcome include

A

1- Intrauterine bacterial infections

2- Decreased blood flow to the placenta

3- Immunologic attack of the placenta by the mother’s immune system

98
Q

Intrauterine infections can lead to

A

Severe retal hypoxia as a result of villus edema (fluid buildup within the placents)

99
Q

__________ decreases in blood flow to the placenta can cause severe fetal damage and even death

A

Chonic and acute

100
Q

Other insults that can adversely affect pregnancy outcome by affecting the function of the placenta

A

1- placental separation

2- cord accidents

3- trauma

4- viral and parasitic infections

101
Q

An enlarged placenta weighing more than 600g and measures more than 4cm

A

Placentomegaly

102
Q

Primary causes for placentomegaly

A

Maternal diabetes and Rh incompatibility

103
Q

The implantation of the placenta over the internal cervical os

A

Placenta previa

104
Q

The placenta normally implants

A

In the body of the uterus

105
Q

___ in ____ pregnancies the placenta implants over or near to the internal os

A

1 in 200

106
Q

The placenta may be considered

A

1-complete or total previa

2-partial previa

3-marginal previa

4-low-lying

107
Q

The cervical internal os is completely covered by placental tissue

A

Complete Previa

108
Q

Placental tissue only partially covers the internal os

A

Partial previa

109
Q

Placental tissue does not cover the os, but its edge comes to the margin of the os

A

Marginal previa

110
Q

Placenta is implanted in the lower uterine segment but the edge does not reach the os

A

A low-lying placenta

111
Q
A

Complete previa as evidenced by 3cm between maternal sacrum and the fetal head

112
Q
A

Ultrasound clearly shows the internal os of the cervix (arrows). The placenta is implanted away from the os

113
Q

A pregnancy is at high risk because of the risk of a life-threatening hemorrhage when complicated by

A

Placenta previa

114
Q

As the pregnancy progresses into the 3rd trimester, two very important changes occur

A

1-The lower uterine segment is developing (thinning & elongating in preparation for labor)

2-The cervix softens and somw dilation can occur

(Cervical dilation may also disrupt the attachment of a placenta located over or near the os)

115
Q

7 risk factors associated with placenta previa

A

1-Advanced maternal age

2-smoking

3-cocaine use

4-prior placental previa

5-multiparity

6-prior cesarean section

7-uterine surgery

116
Q

5 Complications of placenta previa

A

1-premature delivery

2-life-threatening maternal hemorrhage

3-increased risk of placenta accreta

4-increased risk of postpartum hamorrhage

5-IUGR

117
Q

In the 3rd trimester, clinically the patient may present with

A

painless, bright-red vaginal bleeding

118
Q

what percent of patients present with bleeding during the forst 30 weeks

A

25%

119
Q

Because the treatment will be different based on the clinical diagnosis, a diagnosis is imperative when

A

a patient presents with 3rd trimester bleeding

120
Q

If a diagnosis of previa is given, the fetus is preterm and themother is not bleeding heavily, the management may be

A

bed rest

maternal transfusion (if necessary)

close observation

121
Q

______ is needed in the majority of previa cases

A

Cesarean section

122
Q

with ___________ previas, a minority of patients may deliver vaginally

A

MArginal placental previa

123
Q

If the fetus is in a cephalic presentation in the last trimester of pregnancy, examine

A

the fetal head in relationship to the posterior wall of the uterus and the mother’s sacrum

(A distance of less than 1.5cm indicates there will not be enough room for the placenta to be between the fetal head and posterior uterine wall)

124
Q

If there is any question of a placenta previa transabdominally, then the patient should be evaluated with

A

transvaginal sonography

125
Q

_________ is a potentially life-threatening fetal complication of the placenta that occurs when large fetal vessels run in the fetal membranes across the cervical os, placing them at risk of rupture and life-threatening hemorrhage

A

Vasa previa

126
Q

The two most common occurrences of vasa previa are

A

1-Velamentous insertions of the umbilical cord into the placental membranes, which cross the cervix

2-When a succenturiate love is present, and the connecting vessels course over the cervix

127
Q
A

Transabdominal succenturiate

128
Q

Vasa previa is diagnosed with sonography when

A

the implanted fetal umbilical vessels are seen to cover the cervix

(color doppler and endovaginal sonography allow visualization of these vascular structures as they cover the os)

129
Q

3 variants of abnormal penetration of placenta beyond the endometrial lining

A

1-Plaventa Accreta

2-Placenta Increta

3-Placenta Percreta

(Hint: the severity gets worse alphebetically)

130
Q

The chorionic cilli attach to the myometrium without muscular invasion

A

placenta accreta

131
Q

Chorionic villi attach extending further into the myometrium

A

Placenta increta

132
Q

Chorionic villi penetrate through the uterus

A

Placenta percreta

133
Q

The risk of placenta accreta increases in patients with

A

placenta previa and uterine scar from a previous C-section

134
Q

The of placenta increta is

A

10-25% in woman with one previous c-secion (when the placenta is implanted over the scar)

Exceeds 50% in women with placenta previa and multiple c-section deliveries

135
Q

Placenta increta results from the

A

1-underdeveloped decidualization of the endometrium

2-the association of placenta previa reflects the thin, poorly formed decisuas of the LUS and offers little resistance to deeper invasion by trophoblasts

3-the previous cesarean scar permits the trophoblastic invasion

136
Q

High maternal mortality and morbidity are associated with

A

Placenta increta.percreta, so an accurate pernatal diagnosis is critical

137
Q

Almost all cases of placental invasion have an _________ in a women with prior c-section

A

Anterior previa

(Pay careful attention to the placenta and myometrium in any patient with a placental previa and prior history of cesarean. There is usually a loss of the normal interface between the placenta and myometrium)

138
Q

angle the transvag probe ______________ to evaluate the uterine-bladder interface

A

toward the urinary bladder

139
Q

You should evaluate the placenta previa to look for the absenece of

A

hypoechoic subplacental venous channels and myometrium beneath the placenta

140
Q

the placental vessels extend within the urinary bladder in

A

Placenta percreta

141
Q

The presence of one or more accessory lobes connected to the body of the placenta by blood vessels

A

Succenturiate placenta

142
Q

The retention of the succenturiate lobe at delivrey may result in

A

postpartum hemorrhage or infection

143
Q

With succenturiate placenta look for a

A

discrete lobe that has “placenta texture” but is sparate from the main body of the placenta

144
Q

with color flow doppler of a succenturiate placenta

A

vascular bands are seen connecting the lobes

145
Q

The succentturiate placenta varies in appearance; it may be

A

as large as the main lobe and appear as two placentas

146
Q

The attachment of the pacental membranes to the fetal surface of the placenta rather than to the underlying villous placental margin

A

A circumvallate/circummarginate placenta

147
Q

A circumvallate placenta is diagnosed when the placental margin is

A

folded, thickened or elevated with underlying fibrin and hemorrhage

148
Q

_______ may occur within or around the placenta and is more commonly seen than a placental abruption

A

Placental hemorrhage

149
Q

refers to bleeding from the placenta from any cause

A

Placental hemorrhage

150
Q

4 locations of placental hemorrhage

A

1-retroplacental

2-subchorionic

3-subamniotic

4-intraplacental

151
Q

If bleeding subsides hemorrahges are more likely to resolves within

A

the 1st trimester

152
Q

The sonographic appearance of placental hemorrhge varies greatly with the

A

location

size

and age or onset of the hemorrhage

153
Q

If a hemorrhage is present, the echogenicity depends on the age of the hemorrhage;

A

an acute bleed-is similar to the echogenicity of the placenta

Subacute and chronic bleed-becomes more hypoechoic

(a poor outcome is expected if fetal bradycardia is present)

154
Q

The separation of a normally implanted placenta before term delivery

A

Abruptio placenta or placental abruption

155
Q

Placental abruption is a premature placental detachment and occure in

A

1 in 120 pregnancies

156
Q

Bleeding in the __________ occurs with separation

A

dicidua basalis

157
Q
A

Ultrasound showing an abruption. Arrows point to the echolucent collection of blood lateral to the edge of the placenta. P, Placenta

158
Q

The detection of acute abruptions is more difficult because

A

the medium level echogenicity makes them isoechoic to placental tissue

159
Q

__________ may be further classified as retroplacental or marginal

A

Abruptio placenta

160
Q

An expanding hematoma can lead to loss of surface area, placing the fetus at risk for

A

hypoxia and even sudden fetal death

161
Q

9 risk factors for placental abruption

A

1-Maternal hypertension (seen in 50% of severe abruptions)

2-Prior abruption

3-Short umbilical cord

4-Uterine anomaly

5-Myomas

6-Abdominal trauma

7-Placenta previa

8-Tobacco use

9-Cocain use

162
Q

Results from the rupture of spiral arteries and is a “high pressure” blees

A

Retroplacental abruption

163
Q

Is associated with hypertention and vascular disease

A

retroplacental abruption

(If the blood remains retroplacental, the patient has no visible bleeding)

164
Q

the most common type of abruptions and are also known as subchorionic bleeds.

A

Marginal abruption

165
Q

This type of abruption results from tears of the marginal veins and represents a “low pressure” bleed

A

Marginal abruption

166
Q

This type of abruption arises from the edge of the placenta, dissects beneath th eplacental membranes and is associated with little placental detachment

A

MArginal abruption

167
Q

Results from intraplacental hemorrhage cause by breaks in the villous capillaries.

Usually there is little risk to the fetus, although the condition is associated with Rh sensitivity and elevated alpha-fetoprotein levels

A

Intervillous thrombosis

168
Q

The presence of thrombus within the intervillous spaces occurs in

A

one third of pregnancies

169
Q

On ultrasound sonolucencies are seen within the homogeneous texture of the placenta

A

Intervillous thrombosis

The inhomogeneity of the placenta is seen with sonolucent areas within the texture of the placenta (arrows).

170
Q

Discrete lesions caused by ischemic necrosis

A

Placental infarcts

(large infarcts may reflect underlying maternal vascular disease)

171
Q

Common and found in 25% of pregnancies, are usually small with no clinical significance

A

Placental infarcts

172
Q

Commonly known as molar pregnancy; they may be benign or malignant

A

Gestational trophoblastic disease

173
Q

3 gestational trophoblastic diseases

A

1-complete or partial mole

2-choriocarcinoma

3-invasive

174
Q

Clinical symptoms of a gestational trophoblastic disease

A

1-extreme nausea and vomiting (from elevated hCG levels)

2-vaginal bleeding

3-uterine size larger than dates

175
Q

Generally have a diploid karyotype and have no fetal tissue

A

Complete moles

176
Q

Usually have a triploid karyotype and fetal tissue is often present

A

Partial or incomplete moles

177
Q

Ultrasound will show a uterus that is larger than dates, no indentifiable fetal parts and an inhomogeneous texture with various-sized cystic structures within the placenta

Bilateral theca lutein cysts are seen in the ovaries secondary to the hyperstimulation of the elevated hCG

A

complete mole

178
Q

carries little malignant potential, is associated with an abnormal fetus or fetal tissue.

On ultrasound a reduced amount of amniotic fluid is noted without defined fetal parts, the placenta is thick with multiple intraplacental cystic spaces

A

Partial mole

179
Q

A benign vascular tumor of the placenta, large tumors can act as arteriovenous malformations shunting blood from the fetus causing complications

A

Chorioangioma

180
Q

2nd to trophpblastic disease, _________ is the most common “tumor” of the placenta

A

Chorioangioma

181
Q

6 complications with Chorioangioma

A

1-polyhydramnios

2-fetal hydrops

3-fetal cardiomegaly

4-IUGR

5-fetal demise

6-preterm labor (large chorioangiomas)

182
Q

Ultrasound exam shows a circumscribed solid or complex mass that protrudes frome the fetal surface of the placenta, it may be located near the unbilical cord insertion site

A

Chorioangioma

183
Q

A Chorioangioma larger than ______ are usually detected prenatally and are more likey to have complications

A

5cm

184
Q

When a placental mass is seen look for

A

polyhydramnios

hydrops

IUGR

and signd of anemia

185
Q

3 differential considerations for solid placental masses include

A

1-partial hydatidiform mole

2-teratoma

3-maternal tumor metastic to the placenta

OB Pathology (16 decks)

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