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Radiology
Placenta Previa
Built from Obstetric Imaging
What’s inside
11 sections · 72 slides
Overview
- What we will walk through
What placenta previa is
The afterbirth parked in front of the exit
- The idea in one line
- Why it matters
- The landmark that decides everything
- The modern definition
- The old words, and why they were dropped
- Two labels, one landmark
- 5 in 1000
How common, and who is at risk
Common early, rare at delivery
- How often it happens
- The rate is not the same everywhere
- Why most early previas disappear
- How a low placenta moves away
- The biggest risk factor: a previous cesarean
- The rest of the risk list
- The risk factors at a glance
Why it happens
Two ideas, neither of them proven
- The honest answer: nobody knows
- Idea one: the scar holds the placenta down
- Idea two: low oxygen makes a wider placenta
How it shows up
Bleeding, often without any pain
- The classic picture
- The rule that prevents disasters
- A short cervix warns of trouble
- Even a resolved previa leaves a mark
- What it means for the baby
- The newborn problems to expect
- 50-60%
Finding it on ultrasound
One probe screens, the other decides
- Ultrasound is the gold standard
- Placenta covering the cervix, seen through the abdomen
- How good is the abdominal scan?
- Where the abdominal scan lets you down
- Low-lying placenta measured from the internal os
- If the vaginal probe is refused
- Transvaginal ultrasound is the most accurate
- Belly probe versus vaginal probe
- Doing the transvaginal scan safely
- Which way does the placenta spread?
- Placenta covering the os and spreading backwards
- Placenta covering the os and spreading forwards
- When it is found, and when to look again
- How much overlap predicts a previa that stays
- When a previa seems to resolve, check these
- Previa plus an old cesarean: hunt for PAS
- Warning signs of accreta on a previa scan
- What to notice on that scan
- Can you predict who will bleed heavily?
- One more job for the scan
- Where MRI fits
- “
Look-alikes
What else bleeds late in pregnancy
- Other causes of late pregnancy bleeding
- What examination adds, after the scan
- The trap: a clot that looks like placenta
Care before delivery
Counsel, rescan, and never examine blind
- Found at the mid-pregnancy scan: what next
- The order of steps when a pregnant woman bleeds
- First assessment of a bleeding previa
- When bleeding forces delivery
- When it is safe to wait
- How long to keep her in
- When to deliver
One measurement decides the delivery
Placental edge to internal os, in centimetres
- The distance rule
- Three distances, three plans
After the baby is out
The bleeding risk does not end at delivery
- Why the womb keeps bleeding
- Be ready before you start
- What to have lined up
- The surgical options, in plain words
Key points
What to carry out of this topic
- Key points, part one
- Key points, part two
- One-minute recap
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition