Second and Third Trimester- Basic Scan Flashcards

1
Q

The second trimester is what weeks?

A

13-27 (3-6 months)

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2
Q

Between what weeks can performing an ultrasound allow you to image all organs and predict due date?

A

16-26 weeks GA

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3
Q

The spine can be identified sonographically by which week?

A

16-18 weeks

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4
Q

The spine is completely ossified by?

A

Week 18

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5
Q

The 3 ossification centers can be seen by?

A

16 wks GA

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6
Q

What are the 3 ossification centers?

A

2 posterior (laminae) and 1 and anterior (centrum)

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7
Q

The 3 ossification centers are best seen in which plane?

A

Transverse

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8
Q

The central portion of the spine appears how sonographically?

A

hypoechoic

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9
Q

The lumbosacral spine is not completely ossified until?

A

> 18 wks GA

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10
Q

Where can the lateral ventricles be seen?

A

on either side of the midline falx

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11
Q

The midline falx is also called?

A

interhemispheric fissure

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12
Q

The lateral ventricles should not exceed?

A

10 mm

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13
Q

How do you measure the lateral ventricles?

A

inner to inner through the atrium

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14
Q

True or False: Both the normal anterior and posterior horns of the lateral ventricles are seen sonographically

A

False; only posterior horns

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15
Q

Where is hydrocephalus first seen?

A

lateral ventricles (dilated lateral ventricles or ventriculomegaly)

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16
Q

Where is the choroid plexus located?

A

in the lateral ventricles

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17
Q

How does the choroid plexus appear sonographically?

A

echogenic

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18
Q

What is the function of the choroid plexus?

A

produce CSF

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19
Q

By when is the brain anatomy visualized?

A

12-14 wks GA

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20
Q

Where can the thalami be visualized?

A

on either side of the midline

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21
Q

What serves as the landmark for the BPD and HC?

A

thalami, CSP, midline falx

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22
Q

What is the thin echogenic line seen between the thalami?

A

third ventricle

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23
Q

Where can the cisterna magna be visualized?

A

in the posterior fossa posterior to cerebellum

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24
Q

The cisterna magna should never exceed?

A

10 mm

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25
Q

Where is the cerebellum located?

A

in the posterior fossa

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26
Q

How does the cerebellum appear sonographically?

A

two hypoechoic lobes with an echogenic vermis seen between

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27
Q

An absent vermis can cause?

A

splaying of cerebellum

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28
Q

What is the cavum septum pellucidum (CSP)?

A

slit like space that is midline separating the anterior horns of lateral ventricles

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29
Q

How does the CSP appear sonographically?

A

anechoic rectangle in anterior part of the head

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30
Q

Circulation of CSF

A
  1. CSF produced by choroid plexus
  2. Flows through Foramen of Monro to 3rd ventricle (between thalamus)
  3. Aqueduct of Sylvius connects 3rd and 4th ventricle
  4. CSF flows through subarachnoid space through the Foramen of Luschka and Foramen of Magendie
  5. CSF is absorbed into dural venous sinuses via arachnoid villi
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31
Q

The nuchal thickness (nuchal fold) should not exceed?

A

< 5-6 mm

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32
Q

How does CSF appear sonographically?

A

anechoic

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33
Q

By when is the 4 chamber heart identified sonographically?

A

16-18 wks

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34
Q

The apex of the heart should point where?

A

left side of fetus

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35
Q

Which portion of the heart is closest to the chest wall?

A

right ventricle

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36
Q

Which portion of the heart is closest to the spine?

A

Left atrium

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37
Q

The fetal heart should occupy ______ of the chest.

A

1/3

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38
Q

Where is the tricuspid valve located?

A

between the right atrium and right ventricle

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39
Q

Where is the mitral/bicuspid valve located?

A

between left atrium and left ventricle

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40
Q

The foramen ovale shunts blood from?

A

the right atrium to the left atrium

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41
Q

The foramen ovale turns into what when it closes?

A

fossa ovalis

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42
Q

Which portion contains more oxygenated blood?

A

left atrium

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43
Q

What is the normal fetal heart rate?

A

120-160 bpm

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44
Q

A fetal heart rate of < 100 bpm indicates?

A

bradycardia

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45
Q

A fetal heart rate of >180 bpm indicates?

A

tachycardia

46
Q

Which ventricle has thicker walls? why?

A

left; higher forces needed to pump blood through body

47
Q

The fetal stomach is identified sonographically by?

A

Wk 10; better seen by wk 14 due to improvement of fetal swallowing

48
Q

How does the stomach appear sonographically?

A

round, fluid filled structure on left side of fetal abdomen

49
Q

What are the landmarks for AC?

A

stomach, portal vein, spine

50
Q

The gallbladder is identified sonographically at?

A

20 wks GA

51
Q

Where is the gallbladder located?

A

right of midline

52
Q

The fetal adrenal glands have a _______ adrenal cortex and a ______ medulla.

A

hypoechoic; echogenic

53
Q

The fetal kidneys start producing urine when?

A

13-15 wks

54
Q

what structure in the heart can be confused for a fetal anomaly?

A

chordae tendineae

55
Q

What is a major component of amniotic fluid?

A

fetal urine (16-18 wks GA)

56
Q

By when are the kidneys more visible?

A

3rd trimester

57
Q

How do the renal pelves appear sonographically?

A

anechoic slit within central kidney

58
Q

How do the renal pelves appear sonographically?

A

anechoic slit within central kidney

59
Q

The renal pelves should not exceed?

A

6 mm

60
Q

What vessels does the umbilical cord consist of?

A

2 umbilical arteries and 1 umbilical vein (3 vessel cord)

61
Q

The 3 vessels of the umbilical cord creates what sonographically?

A

mickey mouse sign

62
Q

True or false: Some umbilical cords can have 1 umbilical artery and 1 umbilical vein

A

True (2 vessel cord); normal varient

63
Q

What kind of blood do the umbilical arteries carry?

A

deoxygenated

64
Q

The umbilical arteries arise from which vessels?

A

hypogastric arteries

65
Q

The umbilical vein carries what kind of blood?

A

oxygenated

66
Q

The umbilical vessels are encased by?

A

wharton’s jelly

67
Q

True or False: you should image the umbilical cord with color doppler

A

False; can cover defects

68
Q

What is a nuchal cord?

A

umbilical cord encircles fetal neck

69
Q

By when is the bladder identified sonographically?

A

10 wks

70
Q

The fetal bladder fills every ______.

A

30 minutes

71
Q

What can be indicated by a failure to image the bladder?

A

UTI

72
Q

True or False: A UTI can be life threatening to a fetus

A

true

73
Q

What is the measurement for GA in the third trimester?

A

Femur length

74
Q

How do you measure the femur length?

A

measure the diaphysis

75
Q

What is the lateral bone of the lower arm? Medial bone?

A

radius; ulna

76
Q

What is the lateral bone of the lower leg? Medial bone?

A

fibula; tibia

77
Q

True or False: Hands and feet are required for basic guidelines

A

False; not required

78
Q

True or False: BPD and HC are measured on the same plane

A

True

79
Q

Where should the fetal head measurements be taken?

A

at the level of the thalamus and CSP in the axial plane

80
Q

What are the most accurate measurements of the second trimester?

A

BPD and HC

81
Q

How is the BPD measured?

A

from outer edge of partietal bone to inner edge of parietal bone (leading edge to leading edge)

82
Q

How is the HC measured?

A

outer to outer

83
Q

What is OFD?

A

Occipito-frontal diameter

84
Q

When do you use OFD?

A

when head shape is questionable (not oval)

85
Q

Mesocephalic

A

normal shape (70-86% CI)

86
Q

Dolicocephalic

A

long and narrow (<70% CI)

87
Q

Brachycephalic

A

broad and round (>86% CI)

88
Q

Brachycephalic

A

broad and round (>86% CI)

89
Q

Which head shape is associated with Down Syndrome?

A

Brachycephalic

90
Q

What is the CI?

A

cephalic index

91
Q

The AC is measured at what level?

A

level of stomach and junction of umbilical vein and left branch of portal vein

92
Q

True or False: The AC measurement includes fetal skin

A

True

93
Q

True or False: the kidneys and adrenal glands are not included in AC

A

true

94
Q

In the second trimester, what can signify the gender is a boy?

A

turtle sign

95
Q

In the second trimester, what can signify the gender is a girl?

A

hamburger sign

96
Q

Amniotic fluid is 98% ______

A

water

97
Q

What is the function of amniotic fluid?

A

protects fetus, regulates body temperature, allows for movement, aids in development of muscles and skeletal structures

98
Q

What is amniotic fluid critical for?

A

fetal lung development

99
Q

What is the AFI

A

amniotic fluid index

100
Q

How do you measure AFI?

A

divide the uterine cavity into 4 quadrants and measure the deepest pocket of each quadrant then add all 4 measurements

101
Q

What is the normal range of the AFI measurement?

A

> 8 and <24 cm

102
Q

What is SDP?

A

single deepest pocket

103
Q

How do you measure SDP?

A

find the deepest pocket of fluid

104
Q

What is the normal range for the SDP?

A

> 2 and < 8 cm

105
Q

Define polyhydramnios and it’s measurements for AFI and SDP

A

too much amniotic fluid; AFI: > 24 cm; SDP: > 8 cm

106
Q

True or false: polyhydramnios provides good resolution

A

True

107
Q

Define oligohydramnios and it’s measurements for AFI and SDP

A

not enough amniotic fluid; AFI: < 8cm; SDP: < 2 cm

108
Q

True or false: oligohydramnios provides good resolution

A

false; poor resolution

109
Q

SDP is also called?

A

MVP (maximal vertical pocket)

110
Q

What is vernix and how does it appear sonographically

A

normal desquamated skin cells, she’d hair, and sebum; echogenic particles in amniotic fluid

111
Q

What is meconium and how does it appear sonographically?

A

menacing sign of bowel contents in amniotic fluid; grey and hazy

112
Q

What is the formula for CI?

A

BPD/OFD x100