Ch. 52 Test Flashcards
_____ is the absence of one or both eyes
anopthalmos
_____ is abnormally wide spacing of the orbits
hypertelorism
______ is abnormally small eyes
micropthalmos
______ is presence of only one eye
cyclops
_____ is abnormally close spacing of the orbits
hypotelorism
_____ describes an abnormally shaped cerebellum associated with neural tube defects
banana sign
_____ describes an abnormal shape to the frontal bones associated with neural tube defects
lemon sign
_____ refers to a more round shape to the head than usual, resulting in a larger BPD
brachycephaly
______ refers to an elongated shape to the head, resulting in a smaller BPD than expected
dolicocephaly
Fetal age begins at the time of
conception
Gestational age in the world of sonography generally refers to
menstrual age
Give 4 reasons why it is important to know the menstrual age of a pregnancy
- invasive procedure 2. menstrual AFP screening
3. delivery date 4. evaluate fetal growth
The ______ is a hypoechoic area in the fundus of the uterus that is seen at about 4 weeks menstrual age
gestational sac
By 5 weeks, a measurable _____ is seen
gestational sac
At what HCG level should the gestational sac be seen
above 500 mIU/mL
During the first 10 weeks, what is the growth rate for the gestational sac
1mm/day
At what size gestational sac should the yolk sac be seen
> 8mm
Why should an over distended bladder matter when measuring the gestational sac
compression of gest sac
What is the normal size for a yolk sac
<6mm
A gestational sac greater than 8mm is associated with
poor preg outcome
At what gest sac size should cardiac activity be seen
> 16mm
How accurate is the gest sac diameter in predicting gestational age
+/- 2-3 weeks
How accurate is CRL in predicting gestational age
+/- 3-5 days
If the CRL is so much more accurate than the GSD in predicting gestational age, why do we need to measure the GSD after CRL is visible
correlate sac size to embryo size
Cardiac activity should be seen when the CRL is greater than ___ in length
7mm
Absence of an embryo by 7-8 weeks gestation is consistent with
anembryonic pregnancy
If the CRL of the embryo is 15mm, what is the gestational age
7.5 weeks
Why is the CRL no longer accurate after 12 weeks
extension and flexion of fetus
Between 17 and 26 weeks gestation, what is the accuracy of BPD measurements
+/- 11 days
In the late third trimester, what is the accuracy of BPD measurements
+/- 3 weeks
Why does the accuracy of BPD decrease
variations in normal size for gest age
Describe the landmarks and technique for measuring the BPD
outer to inner edge at transverse level of the mid brain (CSP, thalamus, falx)
Describe the landmarks and technique for measuring the HC
measure margins of skull, same as BPD
What is the cephalic index
BPD/OFD x 100
What is the CI used to define
normal shape of fetal head
If the CI is abnormal, should the BPD be included in calculations of gestational age
no
What is the normal range for CI
75-85%
Describe the landmarks and technique for measuring the AC
round trans image with stomach and umbilical portion of left portal vein midline to liver, outer margins of abdomen wall should be measured
What factors can influence the size and shape of the AC
compression, fetal breathing, fetal crowding, oligohydramnios, liver affected by IUGR
Describe the technique for measuring FL
measure blind end to blunt end, greater trochanter to external lateral chondile
Is the FL about as accurate as the BPD in calculating gestational age
yes
Why must the sonographer be especially careful about FL measurements when using a curvilinear probe
tends to shorten femur, bowing
How can the distal formal and proximal tibial epiphyseal ossification centers be used to date a pregnancy
3.3-3.5 weeks
When would the sonographer measure the humerus, tibia, radius, ulna, or fibula during a sonogram
when skeletal dysplasia, abnormal femur measurements and dwarfism are suspected
Why would the use of multiple parameters diminish the accuracy of predicting gestational age when the fetus is not normal
congenital abnormalities of the fetus can alter measurements
Describe the technique for performing the measurement of the binocular distance
lateral to lateral edge (outer to outer}
Describe the technique for performing the measurement of the ocular distance
single orbit diameter
Describe the technique for performing the measurement of the interocular
enter to enter
The fetal cerebellum correlates with gestational age up to
28 weeks
Why would the cerebellum not be used to predict gestational age in the presence of spinal or pleural tube defects
inaccurate due to shape
______ describes a baby that is delivered before 38 menstrual weeks
pre term
______ describes a baby that is delivered after 42 menstrual weeks
post term
_____ describes a baby that is delivered between 38 and 42 menstrual weeks
term
