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Radiology
Monochorionic Diamniotic Twin Gestations
Built from Obstetric Imaging
What’s inside
7 sections · 83 slides
Overview
- What this deck covers
- Why this label matters more than any other in twins
What monochorionic diamniotic means
Two words, two separate questions about the same pregnancy
- Take the name apart
- What that means for the babies
- Twin fetuses separated by a dividing membrane
- These twins are always identical
- Timing of the split decides the plumbing
- From one egg to one placenta and two sacs
- 32.6
- Reading those numbers
- The rare exception to the identical-twin rule
Proving it on ultrasound
One gestational sac, two yolk sacs, and the T sign
- How twins are usually found
- Only the scan can answer the two key questions
- The three findings that define this pattern
- What you see at 6 to 10 weeks
- Count the yolk sacs when the membrane will not show
- Suspect early, confirm later
- Work through three things, in order
- The T sign — what you are looking at
- 100%
- What those numbers mean in practice
- T sign in a late first-trimester twin pregnancy
- The same sign later in pregnancy
- The look-alike sign that means the opposite
- What the membrane insertion tells you
- Two findings that support but do not prove
- Put the features together and accuracy climbs
- Measuring the membrane in midpregnancy
- Thin and two-layered, or thick and multi-layered
- Why the layer count works
- Membrane between monochorionic twins under the microscope
- The dividing membrane of dichorionic twins
- When the membrane vanishes from view
- The stuck twin appearance
Telling it apart from the look-alikes
Dichorionic diamniotic and monochorionic monoamniotic
- What else could it be
- The three twin patterns side by side
- The one with no membrane at all
What can go wrong
The price of sharing one placental circulation
- Risks that every twin pregnancy carries
- The extra problems of one shared placenta
- Where the trouble starts
- Four blood-flow syndromes to know
- Twin-twin transfusion syndrome — the idea
- 15–20%
- Reading those two numbers
- The first thing you notice on the scan
- How it worsens if nothing is done
- The TTTS cascade
- Twins sharing one placenta with vessels crossing between them
- What to notice in that picture
- Early warnings in the first trimester
- Treating TTTS
- When one twin grows much smaller
- Why one twin gets less
- Twin anaemia polycythaemia sequence
- Managing TAPS
- Twin reversed arterial perfusion sequence
- Screening for anomalies and chromosome problems
- Look at the hearts separately
- Checking the cervix for preterm birth risk
- What to do about a short cervix
- The risk of losing a twin before birth
- Why an apparently normal pair is still watched
- 15%
- Why a single demise hurts the survivor
Watching the pregnancy and planning delivery
Serial scans from 16 weeks, then a planned early birth
- How often to scan
- What every surveillance scan must include
- The surveillance timeline
- When to test more intensively
- The last-resort option
- Ultrasound in the delivery room
- When to deliver
- After the babies are born
Summary
What the referring physician needs to know
- What the referring physician needs to know — the risks
- What the referring physician needs to know — the scans
- Key points — what it is
- Key points — how to recognise it
- Key points — what to do about it
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition