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OB review > 2nd & 3rd Tri > Flashcards

2nd & 3rd Tri Flashcards

1
Q

after what week does the pregnancy enter the 2nd trimester?

A

after the first 12 weeks

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2
Q

The early portion of the 2nd trimester can still yield an accurate gestational age using multiple biometric measurements T or F?

A

True

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3
Q

what measurement is no longer acceptable in the 2nd tri?

A

performance of one long-axis measurement (CPL)

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4
Q

By 20 weeks, the primary biometric parameters are? (4)

A
  • biparietal diameter (BPD)
  • head circumference (HC)
  • abdominal circumference (AC)
  • Femur length (FL)
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5
Q

whats concidered the growth stage of pregnancy?

A
  • after midterm or 20 weeks GA
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6
Q

Measurements performed in the late 2nd and 3rd trimesters are more accurate for estimation of?

A
  • gestational size rather than age
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7
Q

what is Biparietal diameter? (BPD)

A
  • as patient enters 2nd tri, fetal caranium and intracranial structures become more evident
  • BPD is considered to be one of the best predictors for GA (second to CRL)
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8
Q

what is BPD?

A
  • biometric measurement performed in the transaxial view of the fetal head just above the level of the ears
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9
Q

BPD guidelines?

A
  1. From the lateral aspect of the fetal head, with the sound beam perpendicular to the interhemispheric fissure, also known as the cerebral falx
  2. The diamond-shaped, hypoechoic thalamus should be seen near the center of the cranium
  3. This view should NOT demonstrate the orbital rims anteriorly or the cerebellum posteriorly
  4. The BPD should be calculated at the widest point of the fetal head at this level
  5. Calipers should be placed on the outer edge of the near-field cranium and the inner edge of the far-field cranium
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10
Q

downfall of BPD?

A
  • fetal head shape may influence the accuracy of the BPD (oligohydramnios or with fetal crowding)
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11
Q

An abnormally widened BPD may be a result of?

A
  • rounded fetal head (brachycephaly)
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12
Q

an abnormaly shortened BPD may be a result of?

A

a flattened head (dolichocephaly)

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13
Q

HC may be calculated using what?

A
  • the BPD and occcipitofrontal diameter (OFD) by using the formula

(D1 + D2) x 1.57

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14
Q

HC is now most often performed using?

A

an ellipse measurement

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15
Q

guidelines of HC?

A
  • performed using the same trv image of the fetal head as the BPD
  • Ellipse tracing should be placed along the outer border of the fetal cranium and should not include the soft tissues of the fetal scalp
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16
Q

HC if helpful in what cases?

A
  • abnormal fetal head shape
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17
Q

what measurement is least influenced by head shape?

A

HC

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18
Q

What is abdominal circumference (AC)?

A
  • GA may be determined but its better used for estimation of the fetal size or weight
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19
Q

AC guidelines?

A
  • obtained with true transverse plane of the fetal abdomen at the level of the umbilical vein junction with the left portal vein
  • should show fetal stomach
  • 3 ossification centers of the fetal spine
  • fetal kidneys should NOT be seen
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20
Q

How to measure AC?

A
  • AC is shown with an ellipse at the level of the fetal stomach (S) and portal sinus (P)
  • Abdomen diameters may be obtained perpendicular to one another in the anteroposterior (AP) and transverse dimensions of the fetal abdomen if ellipse is not available
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21
Q

The AC measurement has limitations for assessment of gestational age when?

A
  • fetal crowding can alter fetal abdo shape and size
  • olihydramnios and advanced GA
  • fetal abdo has large variation during 3rd tri because of biological influences
  • fetal AC is influenced more by fetal size than age, especially in 3rd tri
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22
Q

what is FL?

A
  • FL is 2nd to the BPD in accuracy for prediction of GA in the 2nd tri
  • has little biologic variation in the 2nd tri and least affected by surrounding structures
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23
Q

Complete fetal anatomic surveys should include visualization of both femurs for the presence of ossification and gross symmetry T or F?

A

True

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24
Q

FL guidelines?

A
  • femur closest to the transducer shoild be used in estimation of GA
  • imaged perpendicular to the beams axis
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25
Q

how to image FL?

A
  • follow the TRV plance of the fetal torso from the level of the AC to the pelvic region
  • fetal extremities can be visualized inferiorly to the iliac wings
  • then piviot for long axis
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26
Q

what is occipital frontal diameter- OFD?

A
  • OFD measurement may be used along with BPD to determine the fetal head shape and size
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27
Q

how to measure OFD?

A
  • obtained at the same transvere image as BPD with alipers placed directly on the fetal cranium measuring along the interhemispheris fissure
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28
Q

a comparison of what 2 measurements will generate the cephaic index (CI) with what formula?

A

a comparison of the BPD and OFD

Formula: CI= (BPD/ OFD) x 100

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29
Q

what is a normal cephalic index?

A

76-84 %

- indicates normal fetal head shape

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30
Q

what cephalic index indicated a brachycephalic head shape?

A

> 84

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31
Q

what cephalic index indicated a dolichocephalic head shape?

A

<76

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32
Q

OFD is demonstrated by the caliper line over the?

A

cerebral falx

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33
Q

what can also be used to measure the OFD?

A
  • BPD, HC, and cephalic index
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34
Q

what is binocular measurement?

A
  • At any time during a pregnancy, the fetal head may be found in an extremely low position within the maternal pelvis
  • This position may make an accurate BPD technically impossible, even after patient manipulation
  • If the BPD is unobtainable, the binocular distance may be performed as a secondary parameter in calculation of gestational age
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35
Q

the binocular distance may assist in diagnosis of facial abnormalities, such as?

A

hypotelorism and hypertelorism

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36
Q

what is Transcerebellar (TCD) measurement?

A
  • the posterior fossa region of the fetal head should be evaluated for evidence of pathology (cerebellar hypoplasia)
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37
Q

TCD may be used as a secondary?

A

biometric measurement to assess GA

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38
Q

The cerebellum can be visualized how?

A

be angling the transducer inferiorly in the posterior skull from the plane of the BPD

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39
Q

What can be visualized using the TCD measurement?

A
  • cerebellum
  • cerebral peduncles
  • thalamus
  • from posterior to anterior in the fetal cranium
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40
Q

what are cerebral peduncles?

A
  • link brain stem to thalamus

- tracts of nerve fibers

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41
Q

The cerebellar hemispheres can be identified as what on u/s?

A
  • as 2 hypoechoic circular structures with echogenic borders on both sides of the midline
  • hemispheres are adjacent to a brightly echogenic wedge between them - the vermis

other structures include:

  • cisterna manga
  • nuchal fold
42
Q

how is TCD measured?

A
  • placement of calipers on the most lateral borders of the cerebellar hemispheres
  • this measurement in mm is considered to correlate directly with GA between 15-25 weeks
43
Q

TDC is a measurement in millimeters and is considered to correlate directly with gestational age between what weeks?

A

15-25 weeks

44
Q

Posterior fossa structures in a 2nd trimester fetus include? (3)

A
  • nuchal fold
  • cisterna magna
  • cerebellum
45
Q

where is cisterna megna located?

A
  • in the posterior fossa immediately posterior to the cerebellum
  • largest 1 of 3 openings in the subarachnois and pia mater layers of meninges surrounding the brain
46
Q

what is the AP thickness of cisterna manga?

A
  • does not correlate with GA

- NORMAL <1CM

47
Q

abnormal size of cisterna magna is found to be an early indication of?

A

pathologic conditions:

  • ventriculomegly
  • cerebellar hypoplasia
  • dandy-walker malformation
48
Q

Absence or obliteration of the cisterna magna is a finding associated with?

A

fetal spinal dysraphism

49
Q

purpose of Nuchal fold measurement?

A
  • 2nd tri measurement used to identify fetuses at risk for trisomy 21
50
Q

where is nuchal fold? at what level is it taken?

A
  • is the skin at the posterior edge of the fetal cranium

- A measurement of this skin thickness may be taken at the same image plane as the TCD

51
Q

nuchal fold guidelines?

A
  • capilers must be placed at midline along the outer edge of the cranium and the outer edge of fetal skin
52
Q

nuchal fold thickness associated with trisomy 21?

A

5-6 mm or more between weeks 18 and 24

53
Q

what measurements are seen?

A
  • transcerebellar and cisterna magna
54
Q

atrium of the lateral ventricle are located where?

A
  • located inferior to the level of the BPD

- junction of the anterior, occipital, and temporal horns

55
Q

how are the lateral ventricles measured?

A
  • measured perpendicular to the ventricle walls from/next to the golmus of the choroid plexus to the lateral ventricular wall
56
Q

normal lateral ventricle measurement?

57
Q

choriod plexus produces?

58
Q

what is glomus?

A
  • enlargement of choroid plexus at atria of lateral ventricles
  • secretes CSF
59
Q

what is not included in a lateral ventricle measurement?

A
  • hyperechoic choroid plexus
60
Q

thoracic circumference is used for diagnosis of?

A

potentially lethal fetal abnormalities rather than for GA

61
Q

normal thoracic cicumference?

A
  • slightly smaller in size than the abdomen circumference
62
Q

comparisson of thoracic and abdominal circumference significance?

A
  • may provide valauable info regarding possible pathology

- especially skeletal dysplasia

63
Q

small thoracic to AC ratio?

A

< 0.94 +- 0.05

  • may assist in the assessment for risk of pulmonary hypoplasia
64
Q

thoracic circumference guidelines?

A
  • performed in trv plane of fetal chest at the level of the 4CH
  • heart circumference may be compared with the thoracic circumference
65
Q

what is the normal heart circumference?

A

approx. one third of the thoracic circumference

66
Q

long bone measurements? (5)

A
  • humerus
  • radius
  • ulna
  • tibia
  • fibula
67
Q

what does not determine itself from long bone measurements?

68
Q

what can be identifies with long bones?

A

Identification of pathologic conditions may be possible with comparison of all of these measurements

69
Q

Brachycephaly measurement?

70
Q

cisterna magna measurement?

71
Q

nuchal fold measurement?

A

<5-6 mm between weeks 15 and 19

72
Q

dolichocephaly measurement?

73
Q

thoracic circumference to AC ratio?

74
Q

normal cephalic index?

75
Q

The occipitofrontal diameter may be measured in the second or third trimester of pregnancy. This measurement in conjunction with BPD is best used to?

A

determine fetal head shape (CI)

76
Q

The fetal thoracic circumference should be closely evaluated and compared with the abdominal circumference in the event of a suspected?

A

Skeletal dysplasia

77
Q

The sonographic measurement of what fetal biometric parameter is least influenced by shape?

78
Q

what is biophysical profile?

A
  • indirectly tests for fetal hypoxia
  • Objective means for assessing fetal well-being
  • Fetus is observed for 30 min
79
Q

5 parameters evaluated in biophysical profile?

A
  • fetal tone
  • fetal breathing
  • body movements
  • anmiotic fluid volume
  • nonstress test or placenta grade
80
Q

scoring parameters for biophysical profile?

A 
0= does not exhibit
2= exhibits fully
81
Q

placental grading- grade 0?

82
Q

placental grading- grade 1?

A

occasional parenchymal calcifications (18-29 weeks)

83
Q

placental grading- grade 2?

A

occasional basal calcifications with indentations of chorionic plate (>30 weeks)

84
Q

placental grading- grade 3?

A

significatnt basal calcifications with chorionic plate indentations to the basal layer (>39 weeks)

85
Q

normal fetal tone?

A

one complete episode of flecion to extension and back to flexion

86
Q

normal fetal movement?

A
  • 3 seperate fetal movements within 30 mins
87
Q

normal fetal breathing movement?

A

movement of the diaphragm > or equal to 30s

88
Q

normal AFV?

A

amniotic pocket > 2cm

or

amniotic fluid index >5 cm

89
Q

normal nonstress test?

A
  • exhibits 2 fetal heart accelerations within 20 mins

or

  • placental grade > or equal to 2
90
Q

Nonstress findings, fetal tone, breathing and body movements are markers of?

A

fetal hypoxia

91
Q

Amniotic fluid volume is a marker of?

A

chronic fetal hypoxia

92
Q

Fetal presentations?

A
  • Relationship of the fetal head with the internal cervical os
93
Q

fetal position changes less frequently after what week GA?

94
Q

Nonvertex fetal position after 34 weeks may be predictive of?

A

postitional or placental problems

95
Q

fetal presentations- cephalic or vertex?

A
  • fetal head lies most inferior, closest to cervical os
96
Q

fetal presentations- transverse?

A
  • fetal head and body lie across the maternal abdomen

- check for signs of placenta previa

97
Q

fetal presentations- oblique?

A
  • fetal head and body are lying at a 45 degree angle to the maternal sagittal plane: document location of the fetal head
98
Q

breech presentation?

A

Fetal head is located in the superior portion of the uterus

Presenting part should be determined after 36 weeks’ gestation

99
Q

Frank breech?

A

Fetal buttocks are presenting with the feet near head

Hips flexed and knees extended; most common

100
Q

Complete breech?

A

Fetal buttocks are presenting with the knees bent and feet down
Both hips and knees are flexed; least common

101
Q

what is seen in transverse axial plane? (4)

A
  1. flax cerebri
  2. third ventricle
  3. thalamic nuclei
  4. cavum septum pellucidi
102
Q

HC is measured in a plane that must include?

A
  • cavum septum pellucidi
  • 3rd ventricle
  • thalami
  • tentorium

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