← All decks
Radiology
Trisomy 21
Built from Obstetric Imaging
What’s inside
6 sections · 89 slides
Overview
- What this deck covers
What trisomy 21 is
One extra chromosome, and everything that follows from it
- Chromosomes come in pairs — usually
- An extra copy of chromosome 21
- Who worked it out, and when
- 1 in 800
- Two things move the risk
- Reading the age-and-gestation risk table
- Chance of trisomy 21 by mother's age and weeks of pregnancy
- Prevalence of Trisomy 21 by Maternal Age and Gestational Age
- Prevalence of Trisomy 21 by Maternal Age and Gestational Age (continued)
- Where the extra chromosome comes from
- The three routes explained
- Why an extra chromosome changes so much
What the fetus looks like
Major malformations first, then the small clues
- How often the scan sees something
- Major defect or soft marker?
- The heart is the commonest problem
- Heart defects: the population figures
- Duodenal atresia: the blocked gut
- Two fluid pockets side by side in the upper abdomen
- What a likelihood ratio actually means
- The rest of the findings
- The soft markers at a glance
- Ultrasound features grouped by type
- Ultrasound Features of Trisomy 21
How we screen for it
Blood tests, scans, and where the definite answer comes from
- Screening tells you odds, not answers
- From screen to answer
- The BUN trial
- The FASTER trial
- The second-trimester genetic ultrasound
- A clean scan is reassuring too
- Cell-free DNA screening
- 91.78%
- The catch with predictive values
- How often are major malformations actually seen?
- Minor markers in everyday practice
- A soft marker after a negative cfDNA
- What happens after a marker is found
Marker by marker
What each sign is, how to measure it, and how much it shifts the odds
- Nuchal translucency: what it is
- Measuring the neck fluid and nasal bone in profile
- How well does NT perform alone?
- Where to draw the line
- Thicker NT, wider problem
- Defect risk across bands of neck-fluid thickness
- Risk of Chromosomal and Structural Defects According to the NT Thickness
- Cystic hygroma
- Nuchal fold: the strongest second-trimester clue
- How to measure the nuchal fold
- Thickened soft tissue behind the fetal head
- Nuchal fold: the numbers
- The nasal bone
- How to image the nasal bone
- The first-trimester nasal bone view
- Fetal profile with the nasal bone present
- Fetal profile with no nasal bone echo
- Nasal bone: the numbers
- A small nasal bone counts too
- Ventriculomegaly
- Widened fluid space inside the fetal brain
- Ventriculomegaly: the numbers
- Echogenic intracardiac focus
- Bright spot inside a heart chamber
- Calling it correctly
- Echogenic focus: the numbers
- Echogenic bowel
- Abnormally bright fetal bowel
- Do not create the finding yourself
- Echogenic bowel: numbers and look-alikes
- Pyelectasis
- Fluid in the fetal renal pelvis
- Pyelectasis: the numbers
- Short long bones
- 11×
- The weaker markers
- Where MRI fits
Look-alikes and what to do next
Differential diagnosis, counselling and care after delivery
- Every marker has innocent explanations
- How screening practice has changed
- Acting on a second-trimester marker
- After a confirmed diagnosis
- After the baby is born
- What the referring physician needs to know
- Key points
- Key points continued
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition