Term
| What are some of the reasons we might do a prenatal ultrasound? |
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Definition
To check the viability of the pregnancy
To look at the gestational age
To see if there are multiple gestations
To check the fetal anatomy and growth
To identify high risk situations
To guide invasive procedures
To do a fetal echocardiogram or doppler (which evaluates blood flow) |
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Definition
| Divides into left and right. Therefore, if you were cutting a person’s face, you would cut their face into a left piece and a right piece down the nose. |
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Definition
| Divides things into front and back. Therefore, if you were cutting a person's face, a coronal cut would leave you with a face and the back of a head. |
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Term
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Definition
| Divides things top and bottom. If you were cutting a face transversely, you would have the top part of a face (eyes and forehead) and the bottom part of a face (mouth and nose). |
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Term
| What are some of the limitations of ultrasound? |
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Definition
The more amniotic fluid you have the better the visualization
ultrasound waves don’t pass through air
ultrasound waves have a hard time going through bone
maternal acoustics can get in the way (ie, BMI or uterine differences)
ultrasound cannot rule out all birth defects
diagnostic accuracy can be variable
it can be subjective and needs interpretation
it can give undesired information |
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Term
| What determines the sensitivity of an ultrasound? |
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Definition
The experience of the sonographer
the equipment
the gestational age
the maternal body habitus
the position of the uterus
an institutions threshold of brightness for “calling” a marker
the risk of the abnormality in question
high risk or low risk population
ethnic background |
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Term
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Definition
Poor formation of tissue.
Example is a cleft lip. |
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Term
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Definition
Unusual forces cause tissue to form abnormally.
An example is having too little amniotic fluid or uterine constraint can cause arthrogryposis, or a curving of the joints. |
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Term
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Definition
When there is a breakdown of normal tissue.
An example is amniotic bands and how they can cut off fingers. |
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Definition
| An abnormal organization of cells, or abnormal cells, in the tissue. |
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Term
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Definition
A marked deviation from normal. Therefore, a structural change or a congenital defect in a prenatal setting.
An example is a spina bifida. |
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Term
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Definition
NOT ANOMALIES. These are abnormal findings that increase the chance for a chromosomal abnormality, but they are not birth defects in themselves. They are commonly normal variations in development.
Examples include an increased nuchal translucency, shortened humerus or femur, echogenic bowel, etc. The sensitivity of each marker is low, so you must combine many markers to make the overall sensitivity go up. |
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Term
| What are the first trimester ultrasound markers for Trisomy 21? |
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Definition
1. Nuchal translucency
2. Absent nasal bone
3. Tricuspid regurgitation
4. Abnormal flow of the ductus venosis |
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Term
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Definition
| The length of the fetus from the crown to the rump. The crown rump length has to be a certain amount before you can get a nuchal translucency measurement. |
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Term
| If a first trimester screen is done and the fetus has a large NT, what are the next tests that should be done? |
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Definition
A fetal echo to screen for congenital heart defects. About 40% of all major heart defects are picked up because of NT screening.
Karyotype normal? Check for single gene disorders and Noonan syndrome with a microarray. |
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Term
| What are the second trimester ultrasound markers for Trisomy 21? |
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Definition
1. Nuchal fold thickening
2. Echogenic bowel
3. Shortened humerus or femur
4. Echogenic intracardiac focus (bright spot on heart)
5. Pylectasis (dilation of the renal pelvis)
6. Hypoplastic 5th middle phalynx (underdeveloped pinky)
7. Mild ventriculomegaly
8. Hypoplastic nasal bone
9. Sandal gap
10. Flattened facial profile
More than one marker is seen in 50-70% of Down Syndrome pregnancies. |
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Term
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Definition
| Dilation of the renal pelvis. A second trimester marker for down syndrome. |
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Term
| Hypoplastic 5th middle phalynx |
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Definition
| Underdeveloped fifth finger. A second trimester marker for Down syndrome. |
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Term
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Definition
| A marker in the brain. Dilation of the lateral ventricle. A second trimester marker for Down syndrome. |
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Term
| What are some of the major anomalies associated with trisomy 21 that can be seen on ultrasound? |
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Definition
1. Congenital heart defects
2. Cystic hygroma
3. Hydrops (accumulation of fluid in two or more cavities)
4. Posterior urethral valves (obstruction of the bladder)
5. GI tract defects |
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Term
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Definition
| An example of a GI tract defect that might be one of the anomalies seen in a down syndrome pregnancy. This is a blockage in the duodenal (small intestine) that forms a “double bubble” on ultrasound. |
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Term
| What are markers for Trisomy 18 or 13 in the first trimester? |
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Definition
1. Increased nuchal translucency
2. Hormone levels (low PAPP-A and hCG) |
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Term
| What are the markers for Trisomy 18 in the second trimester? |
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Definition
1. Choroid plexus cysts (cysts that occur in the plexus of the brain)
2. Mega cisterna magna (a larger cistern in the brain)
3. A “strawberry shaped” skull
4. A single umbilical artery (so a two vessel cord instead of a three vessel cord)
5. Polyhydramnios (an excess of amniotic fluid)
You’re not usually thinking about markers, really -- you’re looking for major structural abnormalities |
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Term
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Definition
| An excess of amniotic fluid. Measure in all four quadrants. |
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Term
| What are the anomalies associated with Trisomy 18 in the second trimester? |
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Definition
1. Congenital heart defects
2. Cleft lip or palate
3. Neural tube defects (a “lemon sign” or a “banana sign” in the brain indicate these)
4. Omphalocele (abdominal wall defect)
5. Cystic hygroma or thick nuchal fold
6. Diaphragmatic hernia (abnormal opening in the diaphragm so some intestines are next to the lungs)
7. Renal anomalies
8. Micrognathia
9. Skeletal abnormalities (ie, club foot, rocker bottom foot, clenched hands) |
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Term
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Definition
| An abdominal wall defect where the intestines and liver are outside the body. Smaller usually worse. An abnormality associated with Trisomy 18 and 13. |
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Term
| What are the anomalies associated with trisomy 13? (There are not usually distinct markers, though they share some with trisomy 21 and 18. Mostly look for anomalies) |
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Definition
1. Congenital heart defects
2. Central nervous system abnormalities like neural tube defects or holoprosencephaly
3. Facies (absent nose, proboscis, microcephaly, midline clefts)
4. Urogenital anomalies
5. Polycystic kidneys
6. Omphalocele
7. Cystic hygroma
8. Differences in the extremities (polydactyly, overlapping fingers, club or rocker bottom feet) |
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Term
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Definition
| An abnormality associated with trisomy 13. It is when the forebrain doesn’t develop into two hemispheres. |
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Term
| What prenatal findings are associated with Turner’s syndrome? |
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Definition
| 1. Large, septated cystic hygromas 2. Hydrops/fetal ascites (accumulation of fluid in the fetal stomach) 3. Pleural effusion (excess fluid builds up around the lung) 4. Congenital heart defects 5. Renal anomalies (such as horseshoe kidneys) |
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Term
| What findings are associated with triploidy? |
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Definition
1. A large placenta (XXY) or small placenta (XXX)
2. A “moth eaten” placenta
3. (XXY) small head large body or (XXX) large head small body
4. Club foot, omphalocele, CHD, increased NT, other standard signs
If none of the markers seem to go together, triploidy should be high on your list |
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Term
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Definition
| A ratio assocaited with particular markers used to update risk estimates. Take the previous risk estimate and multiply it by the LR for the marker you found. For example, if the previous risk estimate was 1/100 and you found a nuchal thickening, look up the LR for a nuchal thickening (it's 11). Then Take the previous risk estimate and multiply the two (1/100*11 = 11/100) giving you the new risk estimate. |
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