Second Trimester Notes

Question 1

What is the cavum septum pellucidi?

Answer 1

The space between the leaves of the septum pellucidum.

Question 2

What is the cephalic index?

Answer 2

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

Question 3

What does brachycephalic refer to?

Answer 3

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

Question 4

What does dolichocephalic refer to?

Answer 4

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

Question 5

What is the ductus arteriosus? What does this allow?

Answer 5

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.

Question 6

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

Answer 6

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.

Question 7

What is the falx cerebri?

Answer 7

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

Question 8

What is the foramen ovale?

Answer 8

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

Question 9

What is maternal alpha-fetoprotein?

Answer 9

A blood test to assist in diagnosing certain fetal anomalies.

Question 10

What is meconium?

Answer 10

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

Question 11

What is the railway sign?

Answer 11

Term describing the sonographic appearance of the fetal spine.

Question 12

What is the tentorium?

Answer 12

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

Question 13

What is the thalamus?

Answer 13

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.

Question 14

What is the vermis cerebelli?

Answer 14

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

Question 15

What is the biparietal diameter?

Answer 15

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

Question 16

How is the biparietal diameter measured?

Answer 16

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

Question 17

What is head circumference?

Answer 17

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

Question 18

What is the cephalic index?

Answer 18

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

Question 19

What is abdominal circumference?

Answer 19

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

Question 20

What is femur length?

Answer 20

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

Question 21

What is alpha-fetoprotein (AFP)?

Answer 21

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

Question 22

What are causes of high alpha-fetoprotein? 8

Answer 22

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.

Question 23

What are causes of low alpha-fetoprotein? 6

Answer 23

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.

Question 24

What is the quad screen?

Answer 24

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

Question 25

What is the preparation for transabdominal imaging?

Answer 25

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

Question 26

What are contraindications for endovaginal imaging?

Answer 26

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

Question 27

What is the recommended transducer selection for adults?

Answer 27

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

Question 28

What is the patient positioning for transabdominal imaging?

Answer 28

Supine position.

Question 29

What is the examination protocol for fetal surveillance?

Answer 29

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

Question 30

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

Answer 30

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.

Question 31

What is the significance of the nuchal fold measurement?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

What does the bladder signify in a fetal ultrasound?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

When can renal structures be consistently identified?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What is the abdominal/renal ratio in a fetus?

Answer 41

The abdominal/renal ratio is approximately 3:1.

Question 42

What is the largest organ in the fetal torso?

Answer 42

The liver is the largest organ in the fetal torso.

Question 43

What is the echogenicity of the liver?

Answer 43

The liver is a moderately echogenic structure.

Question 44

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

Answer 44

The left lobe is larger than the right lobe.

Question 45

When can the stomach be reliably visualized?

Answer 45

The stomach can be reliably visualized by 13 gestational weeks.

Question 46

What does the presence of the stomach signify?

Answer 46

The presence of the stomach signifies a normal swallowing sequence.

Question 47

Where is the stomach located?

Answer 47

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

Question 48

What does the umbilical cord insertion look like?

Answer 48

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

Question 49

Where is the placental insertion generally located?

Answer 49

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

Question 50

What is the appearance of the umbilical vein?

Answer 50

The umbilical vein courses superiorly toward the liver.

Question 51

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

Answer 51

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.

Question 52

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

Answer 52

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

Question 53

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

Answer 53

The tangential view is useful in determining craniofacial abnormalities.

Question 54

What is the proportion of the face segments? 5

Answer 54

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

Question 55

When does ossification of long bones begin?

Answer 55

Ossification of long bones begins by 11 gestational weeks.

Question 56

What is the ratio of foot length to femur length?

Answer 56

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

Question 57

When do the iliac wings ossify?

Answer 57

The iliac wings ossify at 12 gestational weeks.

Question 58

When does the ischium ossify?

Answer 58

The ischium ossifies by 20 gestational weeks.

Question 59

What should the rib cage encompass?

Answer 59

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

Question 60

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

Answer 60

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

Question 61

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

Answer 61

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

Question 62

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

Answer 62

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

Question 63

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

Answer 63

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

Question 64

What does the skin line look like?

Answer 64

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

Question 65

What is the function of amniotic fluid?

Answer 65

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

Question 66

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

Answer 66

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

Question 67

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

Answer 67

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

Question 68

What does the cervical os length determine?

Answer 68

The length of the cervix determines its competence.

Question 69

What is the normal length of the cervix?

Answer 69

Normal cervical length varies between 2.5 and 4.0 cm.

Question 70

What is the appearance of the placenta?

Answer 70

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

Question 71

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

Answer 71

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

Question 72

What does the umbilical cord consist of?

Answer 72

The umbilical cord consists of one vein and two arteries.

Question 73

What is the flow direction of the umbilical vein?

Answer 73

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