Chapter 51- Sonography Of 2nd/3rd Trimesters Flashcards
Anatomy is accurately assessed at how many weeks gestation?
18 weeks
First two things to look at during examination:
Fetal position and cardiac activity
Fetal positions change less frequently after ___
34 weeks
Fetal lie is described in relation to
Maternal long axis
Fetus head down:
Vertex/cephalic
Fetal head up:
Breech
Thigh flexed at hips and lower legs extended in front of the body & up in front of the head
Frank breech
Both hip and lower extremities are found in the lower pelvis…needs to be delivered by c-section
Complete breech
Hips extended and one or both feet are the presenting parts closest to the cervix
Footling breach
Imaging of the brain and skull is done in a _____ plane
Transverse
Normal brain parenchyma appears
Hypoechoic
The fetal brain becomes more difficult to visualize as pregnancy progresses because
Calcification of the skull
Fetal head moves deeper in the maternal pelvis
Superior cranial structures include
- Choroid plexus
- Lateral ventricles
Produces cerebrospinal fluid
Choroid plexus
Echogenic been like/tear shaped structures
Choroid plexus
Occasionally small cyst can be seen in the choroid plexus in normal pregnancy. This can also be associated with
Trisomy 18
Cerebrospinal fluid can become trapped during early development resulting in the formation of
CP cyst(s)
The lateral ventricle should measure
Less than 10 mm
The lateral ventricles are measured at the level of the ___ in a transverse plane
Atria
Midline cranial structures
- Cavum septum pellucidum(CSP)
- Midline falx
- Thalamus
- Corpus callosum
Midline hyperechoic line that divides the cranial structures into right and left
Midline falx
Straddles the midline falx, looks like a heart or arrowhead
Thalami
Between the thalami lies the cavity of the
3rd ventricle
Boxed shaped echogenic lines straddling the midline falx
Cavum Septum Pellucidum
The CSP is ___ to the thalamus
Anterior
Hypoechoic structure seen in the transverse plane as the band of tissue between the frontal tissue between the frontal ventricular horns
Corpus callosum
Inferior cranial structures
- Cerebral peduncles
- Circle of Willis
- Cerebellum
- Cisterna Magna
- Nuchal fold
Appears as a highly pulsatile triangular region.
Circle of Willis
Cerebellum is ____ shaped
Peanut
Located directly behind the cerebellum, filled with cerebrospinal fluid
Cisterna magna
A normal cisterna magna measures
3-11mm average— 5-6
In the second trimester the nuchal fold is measured in a plane containing the
Cerebellum and Cisterna Magna(CM)
At 20 weeks or less, a measurement of _____ is normal
5mm or less
Nuchal fold measurement is unreliable after
20 weeks
Fetuses with thickened Nuchal skin are at risk for
Aneuploidy
The fetal ventricular system contains what substance?
CSF
CSF coats the:
Brain and spinal cord
The fetal ventricular system flow:
- lateral ventricles
- foramen Monroe
- 3rd ventricle(between thalami)
- aqueduct of Sylvius
- 4th ventricle
- foramen of Magendi(medial), foramen of Luscha(lateral)
- Cerebral & subarachnoid spaces
- Venous system
The most common type of fetal hydrocephaly
Aqueduct stenosis at the level of the aqueduct of sylvius
Aqueduct stenosis at the level of the aqueduct of sylvius will result in
Excess fluid in the lateral and 3rd ventricles
Inner Orbital Distance(IOD) measurement should be made from
Medial border to opposite medial border
Outer Orbital Distance(OOD) is measured from the
Lateral border to opposite lateral border
Outpouching on brain
Anterior cephaloceles
Small chin:
Micrognathia
Abnormal forehead slope-more prominent than normal
Frontal bossing
Small/absent nasal bone is risk factor for
Aneuoploidy
Large tongue that persistently protrudes outside of the mouth:
Macroglossia
In LONG, the double lines of the spine is referred to as:
Train tracks
In TRANS, the spine will visualize
3 ossification points
Fetal lung tissue appears ____ as pregnancy progresses
More echogenic than the liver
Standard heart exam requires a ____
- 4 chamber view
- views of the right/left outflow tracts
The heart lies more ______ in the fetus than the adult because ___
Transverse
Lungs aren’t inflated
The apex of the heart is directed toward ___
The left anterior chest
Echogenic structure that appears within a cardiac chamber and persists despite changing transducer positions is termed
Echogenic Intracardiac focus (EIF)
Oxygen/nutrient rich blood is carried to the fetal circulation via the
Umbilical vein
This structure when it doesn’t close during development is called a “hole in the heart”
Foramen ovale
There are three circulatory shunts in the fetal heart what purpose do they serve
Protect the lungs from circulatory overload
What are the three circulatory shunt in the fetal heart
- Ductus Venosus
- Foramen ovale
- Ductus arteriosis
Lies inferior to the heart and lungs and superior to the liver spleen and stomach
Diaphragm
The muscle that separates the thorax and abdomen
The diaphragm
What liver lobe is bigger in fetus?
Left
Why is the left liver lobe bigger?
Large quantities of oxygenated blood flows through the ductus venosus to the left lobe
The stomach becomes apparent as early as the ____
11th week
Full stomach should be seen in all fetus is beyond the
16th week
The echogenicity of the bowel is typically _____ than the liver
More echogenic
If fetal bowel is as echogenic as the bone it is termed
Hyperechoic bowel
Hyperechoic Bowel is associated with increased risk for
Aneuploidy
Kidneys can be seen as early as
13 weeks
Abnormal renal pelvis measurements before 20 weeks:
5mm
Abnormal renal pelvis measurements between 20-30 weeks
Greater than 8mm
Abnormal renal pelvis measurements beyond 30 weeks
Greater than 10mm
Fetus generally voids (urine) at least ____
Once an hour
Gender may be appreciated as early as
12 weeks
Female gender best visualized in :
Transverse
Female sign:
Hamburger sign
Fetal labia may appear swollen and edematous due to ___
Circulating maternal hormones
Scrotum/penis are fairly easily recognized in ____
Either plane
Fluid seen around the testicles, is a common finding.
Hydrocele
Male sign:
Turtle sign
Short femur/humerus is associated with increased risk for
Aneuploidy
Hands and fingers should be noted whether they ____
Are clenched or open/close normally
When persistent and abnormal flexion of the ankle is seen, _____ should be expected
Club feet
___________ is required to measure the cervix
Transvaginal
Normal cervix measures _____ in pregnancy
3cm or longer
cervix is shortened, or the internal os appears to have a V or you shape is termed ____
Funneling
You may be able to differentiate the right from left sides by identifying an atomic landmarks such as
Stomach, heart, and spine
Stomach is on the
Left
Heart points to the
Left
Spine is on the
Back
