C7.0: 2nd and 3rd Trim. Biometry

Question 1

when is a nuchal lucency done? wks

Answer 1

11-14 wks

Question 2

how do you measure the nuchal translucency?

Answer 2

inner to inner (echogenic area thru the hypo echoic fluid to echogenic skin)

Question 3

what is a common mistake when measuring a nuchal lucency?

Answer 3

mistaking the amniotic membrane for the nuchal

Question 4

do you zoom when doing a nuchal lucency?

Answer 4

yes

Question 5

what does an increased nuchal lucency indicate?

Answer 5

chromosomal abnormalities
cardiac abnormalities
blood disorders
skeletal dysplasia

Question 6

what nuchal lucency measurement is normal

Answer 6

~3mm

Question 7

what are the routine measurements for 2nd and 3rd trimester?

Answer 7

BPD
occipital frontal diameter (OFD)
cephalic index (CI)
head circumference (AC)
abdominal circumference (AC)
femur length
fetal weight

Question 8

when do you do a BPD?

Answer 8

starting at 12 wks until term

Question 9

when would you use a BPD for dating of preg? how accurate was it?

Answer 9

in the 2nd trimester if dating wasn’t done in the 1st trimester
+/- 7 days in early 2nd trimester

Question 10

what intracranial landmarks are used for the BPD measurement and where are they located in the brain?

Answer 10

falx cerebri (anterior and posterior)
thalami (middle)
cavum septi pellucidi (anteriorly)

Question 11

how should the falx cerebri appear on the US screen?

Answer 11

create a flat line across the screen

Question 12

How do you measure the BPD?

Answer 12

outer to inner edge of the skull bones across the widest part of the head

Question 13

when demonstrating the CSP on US, how should it appear and why?

Answer 13

like a box, not an equal sign… showing the box rules out many fetal abnormalities

Question 14

when imaging the CSP, what landmarks may you see anteriorly?

Answer 14

the anterior horns of the ventricles

Question 15

which three head measurements are taken at the same level?

Answer 15

head circumference, BPD and occipital frontal diameter

Question 16

should the HC be around the outside or inside of the skull?

Answer 16

outside

Question 17

can the OFD and BPD be done at the same time?

Answer 17

yes

Question 18

how do you measure the OFD?

Answer 18

from the outer margin of the frontal bone to the outer margin of the occipital bone.

Question 19

the BPD and OFD are used to calculate what?

Answer 19

the cephalic index

Question 20

how do you calculate cephalic index?

Answer 20

(BPD/OFD) X 100

Question 21

what are the two things that head shape influences?

Answer 21

BPD and estimation of fetal age

Question 22

whats the norm range for cephalic index?

Answer 22

75-85%

Question 23

what is dolichocephaly and brachycephaly?

Answer 23

doli: narrow head
brachy: wide head

Question 24

when is a fetus considered to have dolichocephaly and brachycephaly?

Answer 24

doli: <75%
brachy: >85%

Question 25

what can cause dolichocephaly?

Answer 25

if the baby is breached or has low fluid

Question 26

what 2 measurements can be used to calculate HC? and whats the formula?

Answer 26

BPD and OFD HC= (BPD + OFD) X 1.57

Question 27

how is the BPD measured for the HC calculation?

Answer 27

outer to outer, ONLY for this calculation

Question 28

Is HC more or less dependent on shape than BPD?

Answer 28

less

Question 29

whats the formula for Abdominal circumference and where are the callipers placed?

Answer 29

AC= (AP diameter of abdo + TRANS diameter of abdo) X 1.57 callipers are placed around the outer surface of the skin

Question 30

for which measurements do we use an ellipse?

Answer 30

AC and HC

Question 31

what are the landmarks for where you should take the AC?

Answer 31

``` umbilical vein draining into portal vein (hockey stick) stomach adrenal glands round shape ribs 3 ossification centres of the spine ```

Question 32

what does IUGR stand for?

Answer 32

intrauterine growth restriction

Question 33

whats the most important measurement to determine fetal growth?

Answer 33

AC

Question 34

how should you change your scanning window if youre on the fetal abdomen and you are showing the umbilical vein all the way to the skins surface?

Answer 34

you are too inferior on the anterior aspect of the abdomen

Question 35

how should you change your scanning window if youre on the fetal abdomen and you are showing the kidneys?

Answer 35

you are too inferior on the posterior aspect of the abdomen

Question 36

which structures should be seen when scanning the fetal abdomen? and which are less frequently seen?

Answer 36

live, kidney, GB, vasculature, bladder spleen pancreas

Question 37

list the head to abdomen ratios before 32 wks, from 32-36 wks and after 36 wks

Answer 37

before 32: head > abdomen 32-36 wks: head = abdomen after 36 wks: head < abdomen

Question 38

when is femur length the most accurate?

Answer 38

between 14 and 22 weeks

Question 39

why is it important to measure the femur? | what is considered an abnormal femur?

Answer 39

assess for skeletal and chromosomal abnormalities short for gestation age is abnormal

Question 40

which femur should you measure and what is the most optimal window to measure the femur? which part of the femur do you measure?

Answer 40

the femur closest to the probe make the femur perpendicular to the sound beam only the diaphysis (blunt ends)

Question 41

how do you find the femur?

Answer 41

follow the abdomen down to the iliac bones, move the prove to the anterior aspect of the fetus... rotate until the femur is elongated

Question 42

when are the epiphysis seen?

Answer 42

after 32 weeks

Question 43

list the additional 2nd trimester measurements at are only done once @ the detailed scan

Answer 43

``` cerebellum size nuchal fold cisterna magna size ventricular size binocular distance all long bones ```

Question 44

what is the nuchal fold measurement? how and when do we do it?

Answer 44

thickness of the skin at the back of the neck measure from outer occipital bone to outer skin surface from 16-20 wks

Question 45

what is an abnormal nuchal fold and what % of fetuses with an abnormal measurement will have Down syndrome?

Answer 45

> or equal to 6mm is abnormal 45%

Question 46

how do you measure the cisterna magna and what is the upper limit of normal?

Answer 46

from edge of the cerebellum to inner occipital bone upper of normal is 10mm

Question 47

seeing the cisterna magna rules out what % of spinal defects and DWM?

Answer 47

> 90%

Question 48

how will the cerebellum and cistern mag appear with spinal bifida?

Answer 48

banana shaped.... and you wont see the cisterna magna

Question 49

why do we measure the ventricular atrium/trigone? | and where in the brain to we take this measurement compared to the BPD?

Answer 49

to assess for hydrocephalus (dilation of ventricles dur to blockage slightly more cephalic than the BPD

Question 50

which ventricle do we measure and where?

Answer 50

ventricle furthest from the probe at the parietal occipital fissure

Question 51

whats the upper limit of normal for the trigone?

Answer 51

10mm

Question 52

what should the anterior horns measure at under 24 wks

Answer 52

<20mm

Question 53

what is the trigone/atria?

Answer 53

where the body, temporal horn and occipital horn meet

Question 54

How many ‘soft’ markers are concerning when doing a fetal assessment? why

Answer 54

2+ | they increase the chances that baby has chromosomal abnormalities

Question 55

The yolk sac can often be seen on an EV ultrasound when the MSD is how many mm? The embryo can often be seen on an EV ultrasound when the MSD measures how many mm?

Answer 55

8mm 16mm

Question 56

The yolk is readily visualized on a transabdominal ultrasound when the MSD measures how many mm? The embryo is readily visualized on a transabdominal ultrasound when the MSD measures how many mm?

Answer 56

20mm 25mm

Question 57

when do you use MSD measurement?

Answer 57

4-8wks

Question 58

what is the mean sac diameter of the gest. sac for 6, 7 and 8 weeks? how much does it grow every day?

Answer 58

6: 15 mm 7: 20 mm 8: 30 mm (L+ W+D/3) 1.1 mm

Question 59

when is CRL used? wks

Answer 59

6-13wks

Question 60

when is oligohydraminios used? and how do we find it? | with what value is low fluid suspected?

Answer 60

5.5-9 wks MSD-CRL.... if this value is <5mm

Question 61

when is the CSP seen on US?

Answer 61

18-27 wks

Question 62

if youre showing the equal sign instead of the box for the CSP whats the structure youre actually seeking?

Answer 62

columns of the fornix

Question 63

a normal CSP should be how many times longer than wide?

Answer 63

1.5x

Question 64

can the cerebellum measurement be used to determine gestation age? if yes, when?

Answer 64

yes from 14-22 wks, the size in mm will correspond to gestational age

Question 65

what are the landmarks for where you should take the cerebellar measurement?

Answer 65

cavum septum pellucid and cerebellum with cisterna magna

Question 66

what plane do we use to image the orbits when measuring the orbital distance? how do we measure them? does orbital distance change with gestation?

Answer 66

trans plane through the orbits and the skull. measure outer to outer orbit yes

Question 67

what is hypotelorism and hypertelorism?

Answer 67

hypo: eyes too close together hyper: eyes to far apart

Question 68

which long bones do we always measure in the detailed scan? | when would you measure the others?

Answer 68

femur and humerus only if they look abnormal... looking for skeletal dysplasia

Question 69

are clavicles considered a long bone?

Answer 69

yes

Question 70

why would we do a chest circumference?

Answer 70

sm chest is lethal because lungs cant develop properly

Question 71

are feet and hands effects by skeletal abnormalities?

Answer 71

no

Question 72

can you measure foot length for gestation age?

Answer 72

yes

Question 73

which two boney features can be an indication of Down syndrome?

Answer 73

polydactyl | and an absent or hypoplasic nasal bone

Question 74

b/w what growth percentile in a fetus considered normal?

Answer 74

10-90%

Question 75

whats considered large for GA? | what can it be caused by?

Answer 75

>90% | caused by gestation diabetes or maternal obesity

Question 76

what happens in terms of fetal abdomonal growth if mom has GDM?

Answer 76

abdomen grows faster due to more exposure to glucose

Question 77

whats macrosomia? what are potential complications for baby?

Answer 77

weight >4000g - increased morbidity and mortality b/c they're hard to deliver - baby can become hypoglycaemic post delivery

Question 78

whats considered SGA? what causes it? | what are potential complications for baby?

Answer 78

<10% can be due to IUGR which can be caused by multiple pregancies, placental insufficiency, chromosomal abnormalities increased morbidity and mortality

Question 79

compare symmetrical to asymmetrical IUGR

Answer 79

symmetrical: - all measurements are sm - commonly caused by choromosomal abnormalities - account for 25% of all IUGR - occurs in early 2nd trimester asymmetrical: - head is norm size but abdomen is small - commonly caused by placental insufficiency - 75% of all IUGR - occurs in late 3rd trimester