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Radiology
Placenta Circumvallate
Built from Obstetric Imaging
What’s inside
8 sections · 57 slides
Overview
- What this topic covers
- “
What circumvallate placenta is
The membranes start inside the disc, not at its edge
- Start with a normal placenta
- The two membranes, and their names
- Where the amnion and chorion sit
- The delivered placenta, baby side
- When the membranes start too far in
- The definition, in the book's own terms
- What the grey-white ring is made of
- All the way round, or only part-way
- The flatter cousin: circummarginate placenta
- Two ways the membranes can insert too far in
- Delivered circumvallate placenta, baby side
- Inside the ring, one telling clue
How common it is, and in whom
A condition defined loosely has a loose prevalence
- How often it happens
- Why the reported numbers disagree so much
- Who is at risk
Why it happens
The cause is unclear, but one theory now dominates
- Nobody knows the cause
- The deep implantation theory
- How the ring gets left behind
- The end result on the placenta
What it does to the pregnancy
Bleeding comes first; most pregnancies still end well
- Most pregnancies give no warning
- Why an uncovered rim matters
- From bare rim to early delivery
- Bleeding: the commonest sign
- Placental abruption
- The bleeding does not stop at delivery
- A watery discharge that mimics broken waters
- Early birth and early loss
- Effects on the baby: growth and fluid
- Effects on the baby: the serious end
- 25-50%
- What has been linked to a circumvallate placenta
What ultrasound can and cannot do
Suggestive findings, never proof
- A clinical diagnosis, not a scan diagnosis
- What ultrasound may show
- Curled placental edges on ultrasound
- Curled edge of an anterior placenta
- Curled edges at fifteen weeks
- Thick curled ridge in the second trimester
- Reading the curled ridge
- The tire sign on three-dimensional ultrasound
- Tire sign on three-dimensional ultrasound
- Ultrasound misses it, and misses it often
- If a scan does suggest it
- Working up bleeding with a normally sited placenta
What else it could be
A shelf on a scan has several explanations
- Look-alikes on the scan
- When something juts into the amniotic cavity
- Bleeding in pregnancy: the order of thinking
What to do about it
Watch the growth before birth, the placenta after it
- Before delivery
- After delivery
- What the referring clinician needs to know
- Key points
- Key points, continued
- References
- References (continued)
- Suggested reading
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition