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SONOCAN OB Review > Second Trimester Notes > Flashcards

Second Trimester Notes Flashcards

1
Q

What is the cavum septum pellucidi?

A

The space between the leaves of the septum pellucidum.

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2
Q

What is the cephalic index?

A

A ratio of the cranium derived to determine the normality of the fetal head shape.

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3
Q

What does brachycephalic refer to?

A

A round shape to the fetal cranium; cephalic index 85%.

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4
Q

What does dolichocephalic refer to?

A

An elongated shape to the fetal cranium; cephalic index <70%.

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5
Q

What is the ductus arteriosus? What does this allow?

A
  1. A shunt in the fetal circulation that connects the main pulmonary artery with the descending aorta
  2. Allows most of the blood from the right ventricle to the aorta bypassing the lungs.
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6
Q

What is the ductus venosus? What happens to it following birth?

A
  1. A shunt in the fetal circulation that enables oxygenated blood to pass into the heart bypassing the liver.
  2. Following birth, it becomes the ligamentum venosum.
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7
Q

What is the falx cerebri?

A

A sickle-shaped fold of dura mater separating the two hemispheres of the cerebrum.

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8
Q

What is the foramen ovale?

A

A shunt between the right and left atria that allows some blood to bypass the right ventricle.

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9
Q

What is maternal alpha-fetoprotein?

A

A blood test to assist in diagnosing certain fetal anomalies.

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10
Q

What is meconium?

A

A material that collects in the intestines of the fetus and forms the first stool of a newborn.

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11
Q

What is the railway sign?

A

Term describing the sonographic appearance of the fetal spine.

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12
Q

What is the tentorium?

A

A ‘tent’ structure in the posterior fossa that separates the cerebellum from the cerebrum.

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13
Q

What is the thalamus?

A

One of a pair of large oval nervous structures forming most of the lateral walls of the third ventricle of the brain and part of the diencephalon.

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14
Q

What is the vermis cerebelli?

A

Narrow median part of the cerebellum between the two lateral hemispheres.

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15
Q

What is the biparietal diameter?

A

A two-dimensional measurement that is an accurate predictor of gestational age before 20 weeks.

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16
Q

How is the biparietal diameter measured?

A

Measured in a plane corresponding to the widest position of the head that passes through the third ventricle and thalami.

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17
Q

What is head circumference?

A

A three-dimensional measurement that is a reliable measurement independent of cranial shape.

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18
Q

What is the cephalic index?

A

A three-dimensional measurement devised to determine the normality of the fetal head shape. Mean cephalic index is approximately 78% ± 4.4%.

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19
Q

What is abdominal circumference?

A

A three-dimensional measurement that is a predictor of fetal growth, not gestational age.

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20
Q

What is femur length?

A

A one-dimensional measurement and the long bone of choice because of ease of measurement.

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21
Q

What is alpha-fetoprotein (AFP)?

A

Produced by the fetus and found in the amniotic fluid and maternal serum. Normal values vary with gestational age.

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22
Q

What are causes of high alpha-fetoprotein? 8

A
  1. Underestimated gestational age
  2. Fetus older than expected
  3. Multiple gestations
  4. Open neural tube defect
  5. Abdominal wall defect
  6. Fetal-maternal hemorrhage
  7. Renal anomalies
  8. Fetal demise.
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23
Q

What are causes of low alpha-fetoprotein? 6

A
  1. Overestimated gestational age
  2. Fetus younger than expected
  3. Chromosomal abnormalities
  4. Trrophoblastic disease
  5. Long-standing fetal demise
  6. Chronic maternal hypertension or diabetes.
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24
Q

What is the quad screen?

A

Screens AFP, unconjugated estradiol, free human chorionic gonadotropin (hCG), and inhibin A for chromosomal abnormalities.

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25
Q

What is the preparation for transabdominal imaging?

A

Requires bladder distention. Adult – drink 28 to 32 oz of water 1 hour before examination.

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26
Q

What are contraindications for endovaginal imaging?

A

Any patient who does not or cannot willingly consent to the examination. If the pain becomes too severe, terminate examination.

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27
Q

What is the recommended transducer selection for adults?

A

Use the highest frequency possible to obtain optimal resolution for penetration depth. 3.5 to 5.0 MHz transabdominal.

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28
Q

What is the patient positioning for transabdominal imaging?

A

Supine position.

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29
Q

What is the examination protocol for fetal surveillance?

A

Begin examination with a quick survey of the entire gravid uterus assessing fetal number, position, and viability.

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30
Q

What should be evaluated in the cranial region during a second trimester ultrasound? 7

A
  1. Face profile
  2. Coronal view
  3. Falx, third ventricle
  4. Thalami
  5. Cavum septum pellucidi
  6. Cerebellum/vermis
  7. Atrium of the lateral ventricle.
31
Q

What is the significance of the nuchal fold measurement?

A

Soft-tissue thickness between the calvaria and posterior skin line, accurate between 15 and 21 gestational weeks.

32
Q

What is the normal appearance of the heart in a fetal ultrasound?

A

Occupies about one-third of the thorax, with four anechoic symmetrical chambers divided by uninterrupted septa.

33
Q

What does the bladder signify in a fetal ultrasound?

A

Signifies the genitourinary system is working and should be visualized by 13 gestational weeks.

34
Q

What is the appearance of the kidneys in a fetal ultrasound?

A

Isoechoic or hypoechoic structures located on each side of the spine, consistently identified by 18–20 weeks.

35
Q

What is the significance of the gallbladder in a fetal ultrasound?

A

Visualization peaks around 20–32 gestational weeks, signifying the presence of the biliary tree.

36
Q

When can renal structures be consistently identified?

A

Renal structures can be consistently identified by 18–20 weeks.

37
Q

What is the appearance of renal structures in the sagittal plane?

A

They appear as homogeneous, medium-gray elliptical structures on each side of the spine.

38
Q

What is the appearance of renal structures in the transverse plane?

A

They appear as homogeneous, medium-gray circular structures on each side of the spine.

39
Q

What is the normal amount of fluid in the renal pelvis before 33 weeks?

A

Normal amount of fluid in the renal pelvis is <4 mm before 33 weeks.

40
Q

What is the normal amount of fluid in the renal pelvis from 33 weeks to term?

A

Normal amount of fluid in the renal pelvis is <7 mm from 33 weeks to term.

41
Q

What is the abdominal/renal ratio in a fetus?

A

The abdominal/renal ratio is approximately 3:1.

42
Q

What is the largest organ in the fetal torso?

A

The liver is the largest organ in the fetal torso.

43
Q

What is the echogenicity of the liver?

A

The liver is a moderately echogenic structure.

44
Q

How does the size of the left lobe of the liver compare to the right lobe?

A

The left lobe is larger than the right lobe.

45
Q

When can the stomach be reliably visualized?

A

The stomach can be reliably visualized by 13 gestational weeks.

46
Q

What does the presence of the stomach signify?

A

The presence of the stomach signifies a normal swallowing sequence.

47
Q

Where is the stomach located?

A

The stomach is anechoic and located in the left upper quadrant.

48
Q

What does the umbilical cord insertion look like?

A

The umbilical cord has a smooth insertion into the anterior fetal abdomen superior to the urinary bladder.

49
Q

Where is the placental insertion generally located?

A

Placental insertion is generally located in the midportion of the placenta.

50
Q

What is the appearance of the umbilical vein?

A

The umbilical vein courses superiorly toward the liver.

51
Q

What is the significance of the sagittal view of facial structures?

A

The sagittal view is useful in determining the relationship of the nose to lips, formation of the forehead, chin, and presence of the nasal bone.

52
Q

What can be visualized using the coronal view of facial structures?

A

The coronal view is useful for visualizing orbital rings, upper lip, nasal septum, and maxilla and zygomatic arches.

53
Q

What is the significance of the tangential view of facial structures?

A

The tangential view is useful in determining craniofacial abnormalities.

54
Q

What is the proportion of the face segments? 5

A
  1. The segments containing the forehead
  2. Eyes
  3. Nose
  4. Mouth
  5. Chin each form one-third of the face.
55
Q

When does ossification of long bones begin?

A

Ossification of long bones begins by 11 gestational weeks.

56
Q

What is the ratio of foot length to femur length?

A

The ratio of foot length to femur length is 1:1.

57
Q

When do the iliac wings ossify?

A

The iliac wings ossify at 12 gestational weeks.

58
Q

When does the ischium ossify?

A

The ischium ossifies by 20 gestational weeks.

59
Q

What should the rib cage encompass?

A

The rib cage should encompass more than one-half of the chest on either side.

60
Q

What does the spine look like near the base of the skull?

A

The spine widens near the base of the skull and tapers near the sacrum.

61
Q

What is the appearance of the spine in the coronal plane?

A

In the coronal plane, the spine appears as three parallel hyperechoic lines.

62
Q

What is the appearance of the spine in the sagittal plane?

A

In the sagittal plane, the spine shows two ossification centers and two curvilinear hyperechoic lines.

63
Q

What is the appearance of the spine in the transverse plane?

A

In the transverse plane, the spine has three equidistant ossification centers surrounding the neural canal.

64
Q

What does the skin line look like?

A

The skin line appears as an echogenic smooth line posterior to the spine.

65
Q

What is the function of amniotic fluid?

A

Amniotic fluid surrounds and protects the fetus and provides important information on fetal renal and placental function.

66
Q

When does the fetus become the major producer of amniotic fluid?

A

The fetus becomes the major producer of amniotic fluid through swallowing and urine production after 16 weeks.

67
Q

What is the normal range for the amniotic fluid index (AFI)?

A

The normal range for the amniotic fluid index (AFI) is 6 to 24 cm.

68
Q

What does the cervical os length determine?

A

The length of the cervix determines its competence.

69
Q

What is the normal length of the cervix?

A

Normal cervical length varies between 2.5 and 4.0 cm.

70
Q

What is the appearance of the placenta?

A

The placenta appears as an echogenic disk-shaped mass of tissue, hyperechoic compared with the myometrium.

71
Q

What is the normal thickness of the placenta before 24 weeks?

A

The normal thickness of the placenta is ≤4 cm before 24 weeks.

72
Q

What does the umbilical cord consist of?

A

The umbilical cord consists of one vein and two arteries.

73
Q

What is the flow direction of the umbilical vein?

A

The flow of the umbilical vein is directed from the placenta to the fetus.

SONOCAN OB Review (22 decks)

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