Module 15: Nuchal Transluency Flashcards
What is nuchal translucency?
The sonographic appearance of subcutaneous accumulation of fluid behind the fetal neck in the first trimester of pregnancy
In terms of Nuchal translucency, The term translucency is used irrespective of what?
Whether it is septated or not and whether it is confirmed to the neck or envelopes the whole fetus
The incidence of chromosomal and other abnormalities is related to NT how?
Size rather then to NT
In terms of NT, during the second trimester, the translucency usually does what? In a few cases what happens?
Resolves and in a few cases it evolves into either nuchal edema orcystic hygromas with or without generalized hydrops
In a fetus with a chromosomal abnormality the nuchal fluid begins to increase at what weeks?
11 weeks
What other abnormalities can we sonographically appreciate at 11 weeks? 2
- Acriana
- Omphalocele
When does a skull finish ossifying?
Skull ossified around 11 weeks
Omphalocele is normal to have midgut hernia from what weeks? But not after what weeks?
- 8-10 weeks
- 11-12 weeks
In a fetus with a chromosomal abnormalities, the nuchal fluid can decrease after how many weeks?
14 weeks
Patients can have 1st trimester termination if what is found?
An abnormality
It is more difficult to obtain NT after how many weeks? Why?
- 14 weeks
- More vertical fetal position
Do not proceed to perform a NT when what happens? Why?
- If the CRL is over 84mm
- The Test is not valid on a fetus that is over 13w6d
NT on its own is how accurate?
80%
Nuchal translucency with 1st trimester blood work is how accurate?
90%
What are some 1st trimester blood work tests? 3
- bHCG
- PAPPA
- OSCAR
What is OSCAR?
One stop clinics for early assessment of fetal risk - which have 30 minute lab processing time
Nasal bone is not visible in 60-70% of fetus with what?
T21
What disorders are associated with increased nuchal translucency? 7
- Chromosomal defects
- Cardiovascular defect
- Pulmonary defect
- Skeletal dysplasia
- Congenital infections
- Haematological disorders (anemia)
- Metabolic disorders (hypoproteinemia)
What position should the baby be when we measure CRL? 4
- Spine anterior or posterior
- Midline sagittal plane
- Do not use coronal plane
- Fetus should be in a neutral position
What is the Minimum CRL?
45mm (11w)
What is the maximum CRL?
84mm (13w6d)
What is the criteria for CRL? 5
- Magnification
- Position
- Amnion
- Measurement area
- Calliper placement
What is the protocol for NT? 5
- Magnify/zoom only chest and head on image
- Perfect midline sagittal plane
- Neutral flexion of the spine
- Technical settings - decrease compression
- Measure on to on
When we are going through the NT protocol, and look at neutral flexion of the of the spine, what do we need to see? 2
- Chin not on chest
- Chin not high off chest
When we are doing a magnification of NT what must we see? What should the depth of the screen?
- Only fetal head and thorax on image
- About 3-4 cm depth on screen
What is the position the baby should be when we are doing NT? What do we need to see? 3
- True sagittal on fetus
- Fetus in neutral position
- Nasal bone an nuchal together
Why do we need to see the fetus on neutral position during NT scans? 3
- Hyperextension can create a 0.6mm increase in NT
- Flexion can create a 0.4 decrease in NT
- Head turned can increase NT as well
What should the fetus position and the amnion look like?
The fetus should be lifted off the amnion
What is the measurement area for NT? 2
- Widest position of the NT
- Anywhere from the occipital to the thorax
What affects the risk assessment of NT? 5
- Maternal age
- CRL
- Nuchal translucency
- Blood analysis
- Fetal heart rate (<170 beats/min)
Computer program also gives a risk assessment
What ratio is considered a positive risk?
1/300 or less
Just being how old will give you a positive risk no matter the NT?
40 years
What can assist in making your results for abnormalities negative?
Blood work
What is offered if there is a risk in pregnancy?
Amniocentesis
Amniocentesis has a pregnancy loss rate of what?
About 1/200
The NT normally increase with gestational age up to what time?
14 weeks
During scans what should we image? 6
- Heart rate
- Cranium
- Abdominal wall
- Bladder
- Stomach
- Limbs
If we suspect a nuchal umbilical cord, the nuchal measurement is then taken where? What else must we do? 3
- Above and below the nuchal cord
- The measurement is then averaged
- Use colour doppler to confirm location of the cord
If suspect multiple gestations what must we do? Why?
- Assess chorioncity and amnionicity
- This is the best time to see the membranes, later on this may be very difficult to assses
Label
Label
What does these images represent?
Nasal vs. Absent
What does this image represent?
CRL
What does this image represent?
Proper placement of callipers for NT
What s this an image of?
Proper NT measurements
What does this image represent?
Proper magnification for NT
What is the image pointed to?
Amnion
Fill in the chart.
99% for both measurements are what?
3.5mm
Fill in the chart
What does this image represent?
Suspect a nuchal umbilical cord
