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Radiology
Vasa Previa
Built from Obstetric Imaging
What’s inside
9 sections · 49 slides
Overview
- What this covers
What vasa previa actually is
Start with where the cord vessels are supposed to run.
- How the cord normally connects
- When the vessels run bare
- A cord that ends in the membranes
- Vasa previa in one line
- Two roads to the same danger
- What each type means
- Why this can kill in minutes
How common, and in whom
Rare overall, far less rare in the pregnancies you already worry about.
- 1/1300
- Reading those numbers
- What raises the risk
- Making sense of the risk list
How the vessels end up there
The cord does not move — the placenta grows away from it.
- How a central cord ends up bare
- Why the insertion drifts
How it shows itself
Once it bleeds you are already late — which is the whole argument for screening.
- The classic emergency
- The heart rate clue
- How most cases turn up today
Finding it on ultrasound
A fixed sequence: look, switch probe, add colour, add pulsed Doppler.
- The scanning sequence
- Step one: study the cord insertion
- Switching to a transvaginal view with colour
- What it looks like on the screen
- A dark linear vessel tracked over the cervix
- Proving the dark line is a vessel
- Fetal vessels arching across the internal os
- The artery waveform
- The vein waveform
- Vasa previa or a loop of free cord?
- The look-alikes
- How good is the scan?
- What finding it early buys the baby
Other imaging
Useful in a few situations — neither replaces the Doppler scan.
- Where MRI fits
- What MRI showed in one reported case
- Three-dimensional ultrasound
Managing a diagnosed vasa previa
Deliver before the membranes do it for you.
- Who gets screened, and when
- Be honest about the evidence
- The third-trimester plan
- Admission between 30 and 34 weeks
- Monitoring at home instead
- When to deliver sooner
- The planned caesarean window
Take home
Five things worth carrying out of this topic.
- Key points
- Classic signs to remember
- Suggested readings
- Suggested readings (continued)
- References
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition