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OB > Placenta & Fetal Heart > Flashcards

Placenta & Fetal Heart Flashcards

1
Q

What is the only organ that is temporary?

A

placenta

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2
Q

What is crucial to the well being and survival of the fetus?

A

placenta

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3
Q

What are the functions of the placenta?

A

respiration, nutrition, excretion, protection (prevents harmful substances from going to fetus), storage (nutrients), and hormonal function

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4
Q

What hormones are produced by the placenta?

A

neuropeptides, hCG, human placental lactogen, estrogen, and progesterone

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5
Q

Describe the normal appearance of the placenta when it’s delivered?

A

discoid in shape, 15-20cm in diameter, less than 4cm thick (average is 2-2.5cm with center being thickest), around 600g in weight, dark red with blue/purple hint

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6
Q

What is the sonographic appearance of a normal placenta?

A

smooth borders with position either fundal, anterior, or posterior, 2-3cm in thickness of fetus older than 23 weeks

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7
Q

What is a normal sonographic appearance of the fetal placental surface?

A

echogenic chorionic plate along the placental surface adjacent to the amniotic cavity

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8
Q

What is the normal sonographic appearance of the maternal/basal placental surface?

A

location is at the junction of myometrium and the substance of placenta; appears as a hypoechoic band due to endometrial veins running behind the basal plate

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9
Q

How does the appearance of the placenta change sonographically throughout pregnancy?

A

appears as homogeneous medium gray between 8 and 20 weeks gestation; after 20 weeks, intraplacental sonolucencies and placental calcification may begin to appear and placental lakes change in size and shape with maternal position

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10
Q

What is placenta infarction?

A

focal discrete lesion caused by ischemic necrosis

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11
Q

What is found in nearly 25% of pregnancies that is usually small with no clinical significance?

A

placenta infarction

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12
Q

What may large infarctions reflect?

A

underlying maternal vascular disease

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13
Q

What is the sonographic appearance of a grade 0 placental infarct?

A

normal appearing placenta, no calcifications, smooth chorionic plate

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14
Q

What is the sonographic appearance of a grade 1 placental infarct?

A

the basal layer becomes hypoechoic (or anechoic) with few scattered calcifications and subtle indentations of the chorionic plate
this is a normal finding after 34 weeks gestation

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15
Q

What is the sonographic appearance of a grade 2 placental infarct?

A

has larger indentations of the chorionic plate with few linear densities at the basal plate and “comma like” echodensities in the parenchyma
this is a normal finding after 36 weeks gestation

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16
Q

What is the sonographic appearance of a grade 3 placental infarct?

A

there are complete indentations of the chorionic plate with large bright calcifications and placental parenchyma highly echogenic with anechoic areas
this is a normal finding after 38 weeks gestation

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17
Q

Where is the umbilical cord usually attached in the placenta?

A

near the center

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18
Q

What arteries increase in size during pregnancy?

A

uterine arteries

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19
Q

In the first trimester, what does the uterine artery show sonographically?

A

high resistance flow patterns

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20
Q

In the second trimester, what does the uterine artery show sonographically?

A

low resistance flow pattern (more so in late second and third trimesters; decreasing resistance in early second)

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21
Q

Normal trophoblastic invasion of spiral arteries show what type of Doppler pattern?

A

low resistance

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22
Q

What is a battledore placenta?

A

insertion of umbilical cord into the margin of placenta (not central portion), within 10mm of the edge

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23
Q

What is a velamentous placenta?

A

cord inserted into the membrane and not in the thickness of the placenta

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24
Q

What are the risks associated with a velamentous placenta?

A

blood vessels are not protected and can easily be damaged, the cord lies across the cervix (vasa previa) and can be damaged during child birth

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25
Q

What are the risks associated with a bilobed placenta?

A

can increase risk of retained portions of placenta (which can lead to a life threatening infection), increased risk of placenta previa (placenta over internal os), and/or no significance

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26
Q

What is a succenturiate placenta?

A

an addition lobe of the placenta, but of a different size

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27
Q

What are the risks associated with a succenturiate placenta?

A

retension of small lobe (results in infection), previa or vasa previa (blood vessels across the internal os), and/or blood vessel rupture and catastrophic hemorrhage

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28
Q

What is a circumvallate/circummarginate placenta?

A

the attachment of the placental membranes to the fetal surface of the placenta rather than to the underlying villous placental margin
the basal plate is larger than the fetal placenta;

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29
Q

What is the difference between circumvallate and circummarginate placental shapes?

A

the thickness of the ring;

circumvallate has a thicker ring causing the borders to be rolled while circummarginate has a thinner ring

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30
Q

What is the risk of a circumvallate/circummarginate placenta?

A

placental abruption resulting in catastrophic hemorrhage

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31
Q

What is placenta previa?

A

the abnormal implantation of the placenta in the lower uterine segment overlying or near the internal cervical os

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32
Q

What are the different types of placenta previa and how is it determined?

A

low-lying placenta, marginal previa, complete previa, and central previa
determined by how far it is from the internal os (edge of placenta to the internal os)

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33
Q

Describe each type of placenta previa.

A

complete: covers cervical os
partial:
marginal: comes right to the border
low lying: not in direct contact (less than 5cm or less than 2cm)

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34
Q

How does placenta previa occur?

A

One theory is the lower uterine segment stretches out while the placenta stays in place. Another theory is the placenta area doesn’t have enough blood flow and atrophies. Uterine scarring may also be associated.

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35
Q

What are the risk factors for placenta previa?

A

prior c-section and uterine surgeries, advanced maternal age, smoking, prior placenta previa, multiparity, multifetal pregnancies

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36
Q

What are placenta previa complications?

A

maternal catastrophic hemorrhage (during labor), preterm delivery, preterm premature rupture of membranes, intrauterine growth restriction, malpresentation, vasa previa, perinatal death

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37
Q

What are the clinical implications of placenta previa?

A

sudden PAINLESS vaginal bleeding

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38
Q

If placenta previa is suspected, should a vaginal examination be done?

A

No, it can cause catastrophic hemorrhage

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39
Q

If placenta previa is suspected, should a transvaginal exam be done?

A

If needed; the probe is introduced into the anterior fornix, not the cervix and for best information the probe should be 2-3cm away (meaning it is safe)

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40
Q

If placenta previa is suspected, should a transabdominal ultrasound be done or a transvaginal one?

A

transvaginal is favored over transabdominal; it is much more accurate, the cervix is easier to see (vs TA where fetal head may obscure cervix)
but if the bladder is full, it can give a false impression of previa

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41
Q

What is vasa previa?

A

the presence of abnormal fetal vessels within amniotic membranes that cross the internal cervical os

42
Q

What risk is associated with vasa previa?

A

potentially life-threatening fetal complication, vessels at risk of rupture and life-threatening hemorrhage

43
Q

What are the common causes of vasa previa?

A

velamentous insertion of umbilical cord into placental membranes, which cross over the cervix and the presence of succenturiate lobe and connecting vessels traverse the cervix

44
Q

If delivery is imminent with vasa previa, what can this result in?

A

unsupported fetal vessels are prone to tear as the cervix dilates which can result in exsanguination of fetus
(c-section can help prevent this)

45
Q

What is placental invasion?

A

abnormal penetration of placental tissue beyond the endometrial lining of the uterus

46
Q

What are the risk factors of placental invasion?

A

prior c-section, D&C, advanced maternal age, grand multiparity

47
Q

How is placental invasion classified?

A

it is based on the extent of invasion

48
Q

What is placenta accreta?

A

the superficial invasion

the chorionic villi attach to the myometrium without muscular invasion

49
Q

What is placenta increta?

A

the further extension of the chorionic villi into the mymetrium

50
Q

What is placenta percreta?

A

penetration of the chorionic villi through the uterus

it can penetrate through the uterine wall, rectal wall, or bladder wall

51
Q

What are the symptoms to placenta percreta?

A

rectal bleeding or blood in urine

52
Q

What is the best imaging modality to image placenta percreta?

A

MRI

53
Q

With placenta increta/percreta, what is the associated outcome?

A

high maternal mortality and morbidity

54
Q

Two-thirds of women require a peripartum hysterectomy when they have what?

A

both a placenta previa and an associated accreta

55
Q

What happens if the physician removes the placenta manually?

A

maternal shock (3-5L of blood loss), renal failure, death

56
Q

What are the sonographic features of placental invasion?

A

loss of normal retroplacental space, anomalies of the bladder-myometrium interface, prominent placental lacunae (swiss cheese appearance, irregular shape, turbulent color flow), increased vascularity at the interface of the uterus and bladder

57
Q

What is placental abruption?

A

premature separation of the normally implanted placenta from uterine wall, resulting in hemorrhage between the uterine wall and placenta
(results in lack of oxygen to the fetus and a high risk for fetal death)

58
Q

What are the risk factors for placental abruption?

A

hypertension, advanced maternal age (starting at age 35), previous placental abruption, multiparity, uterine distension, multifetal pregnancies, polyhydramnios, (can lead to) vascular deficiency, diabetes mellitus, cocaine use, methamphetamine use, cigarette smoking, alcohol abuse, short umbilical cord

59
Q

What are precipitating factors of placental abruption? In other words, what factors provoke this?

A

trauma, auto accident, sudden uterine volume loss, delivery of first twin, preterm premature rupture of membranes

60
Q

Clinically, what does placental abruption look like in the third trimester?

A

PAINFUL uterine bleeding, strong contractions, fetal distress, may be asymptomatic

61
Q

What are the three types of placental abruption?

A

external abruption (accounts for 80% of cases), relatively concealed abruption (more dangerous because blood clots on maternal surface of placenta - accounts for 20%), concealed abruption

62
Q

With placental abruption, what is the diagnosis made from?

A

primarily clinical symptoms

ultrasound is performed to rule out placenta previa

63
Q

The sonographic findings for placental abruption are…

A

thickening of the placenta, hematoma between placenta and uterus (older hematomas tend to be hypoechoic compared to placenta)
separation of placenta substance from the uterine wall - sonographic clue

64
Q

What is the most common type of placental abruption?

A

marginal abruption

65
Q

What is another name for a marginal abruption?

A

subchorionic bleeds - venous low pressure bleed

66
Q

What is the result from a tear of the marginal vein?

A

hemorrhage and represents as low pressure bleed

67
Q

Where in the placenta does a marginal abruption take place? Is there placental detachment?

A

arises from edge of placenta, dissects beneath placental membranes and is associated with little placental detachment

68
Q

With marginal abruption, where does subchorionic hemorrhage occur?

A

subchorionic hemorrhage accumulates at site of the separation from placenta
it may continue to bleed after initial hemorrhage when blood tracks behind the membranes and through cervix

69
Q

To identify a marginal abruption, what should be done sonographically?

A

carefully scan along edge of placenta to identify a marginal abruption

70
Q

What is the most common tumor of the placenta?

A

chorioangioma

71
Q

What is a chorioangioma?

A

a benign vascular tumor of the placenta; usually small
consists of benign proliferation of fetal vessels; majority are capillary hemangiomas that arise beneath the chorionic plate

72
Q

What are the three histological types of chorioangioma?

A

angiomatoid (characterized by numerous blood vessels), cellular (with poor vascularization), degenerative

73
Q

What are fetal complications of a large chorioangioma?

A

polyhydramnios, hydrops, anemia, cardiomegaly, intrauterine growth restriction, demise

74
Q

Why do large large chorioangiomas cause complications?

A

large tumors act as arteriovenous malformations shunting blood from fetus

75
Q

What is the sonographic appearance of a chorioangioma?

A

located near insertion of the cord and protrudes into amniotic cavity; often presents hypoechoic, rounded mass near chorionic plate; usually contains cystic areas and distinctly different than surrounding tissue; heterogeneous areas (caused by degenerative processes/internal hemorrhage); low resistance pulsatile flow; large tumors may undergo infarction with decreased echogenicity, decreased tumor volume and decreased blood flow

76
Q

What is the cephalic index?

A

determines the normality of the fetal head shape

CI = BPD / OFD x 100

77
Q

What is a normal cephalic index?

A

the range of normal is 75% to 85%

78
Q

What is brachycephaly?

A

head is elongated in transverse plane (BPD) and shortened in the anteroposterior plane ( OFD)
CI greater than 86%

79
Q

What is dolicocephaly?

A

head is shortened in transverse plane (BPD) and elongated in the anteroposterior plane ( OFD)
CI less than 70%

80
Q

Describe the lay of the fetal heart.

A

lies more transversely, apex (compesed of LV) directed toward left anterior chest, right ventricle closest to chest wall and left atrium closest to spine

81
Q

What should be assessed with the four chamber heart view?

A

the apex/direction it’s pointing to, four chambers, chamber size, integrity of interventricular septum (should see septum primum and flap of foramen ovale)

82
Q

Describe the four chamber heart view.

A

ventricles should be same size (or RV UPTO 20% larger), echogenic moderator band (in RV), septum leaflet of tricuspid is slightly inferior to mitral

83
Q

What should be assessed when viewing the left outflow tract?

A

continuation of the aortic walls (interventricular septum continuous with anterior wall; mitral valve leaflet continuous with posterior wall), flow from LV to Ao, and the position of the aorta coming from the left ventricle

84
Q

What should be assessed when viewing the right outflow tract?

A

size of aorta and pulmonary trunk and flow from RV to pulmonary trunk

85
Q

What is the relationship between the RVOT and LVOT?

A

criss-cross pattern

86
Q

What is the echogenic structure that appears as bright as bone in the cardiac chamber?

A

echogenic intracardiac focus

may be associated with risk of aneuploidy and cardiac defects

87
Q

What does the fetal diaphragm look like sonographically?

A

sonolucent linear structure separating thorax from abdomen

88
Q

What is the direct vascular link to the fetal heart?

A

ductus venosus

89
Q

What is a reflection of fetal growth?

A

the liver

90
Q

When does the stomach becomes apparent in fetal growth?

A

11th week

full stomach should be seen in a fetuses at 16 weeks

91
Q

Describe the relationship between fetal bowel and liver.

A

echogenicity of fetal bowel typically greater than echogenicity of fetal liver

92
Q

What is hyperechoic bowel in a fetus?

A

when bowel is as echogenic as bone

this is associated with increased risk of aneuploidy (specifically trisomy 21)

93
Q

When are fetal kidneys apparent with ultrasound?

A

13 weeks

94
Q

List the renal pelvis measurements of fetal renals and their significance.

A

> 5mm before 20 weeks
8mm between 20 and 30 weeks
10mm beyond 30 weeks considered abnormal

95
Q

When is it common to see extra fluid in renal pelvis of fetus?

A

when there is extra amniotic fluid and when mother has full bladder
associated of persistent mild bilateral renal pelvis dilation known as pyelectasis and aneuploidy

96
Q

How often does a fetus urinate?

A

at least once every hour

97
Q

When can gender be identified in a fetus?

A

as early as 12 weeks

98
Q

What are sonographic signs for determining genders.

A

female: hamburger sign
male: tortoise sign

99
Q

What is a short femur and humerus associated with in a fetus?

A

aneuploidy

100
Q

Why is it important to observe the fetal hands if anomaly is suspected?

A

clenching of hands is common in chromosomal disorders, such as in trisomy 18

101
Q

1 to 2 days after birth, what do certain fetal vessels become?

A 
ductus arteriosus - ligamentum arteriosum
umbilical vein - ligamentum teres
ductus venosus - liagamentum venosum
umbilical arteries - remnant
foramen ovale - fossa ovale

OB (10 decks)

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