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Radiology
Diagnostic Procedures in Multiples
Built from Obstetric Imaging
What’s inside
9 sections · 70 slides
Overview
- What you will learn
Why twins change the plan
More risk, two babies, and one shared decision
- Twins carry more risk than singletons
- Twins come in two kinds
- Why two eggs means more risk
- One egg: same recipe, different risk profile
- If one is affected, usually both are
- The two diagnostic tests side by side
- Amniocentesis under ultrasound guidance
- Chorionic villi and decidua compared
- Why the villi matter
Before the needle goes in
Who does it, what is said, and what is given afterwards
- Only an experienced operator should do this
- What the patient must be told
- The extra conversation twins need
- Rhesus protection afterwards
- One sac or both in identical twins?
- A karyotype with three copies of chromosome 21
- The reports that changed practice
- So sample both sacs
Chorionic villus sampling in multiples
Placental tissue, first trimester, two routes
- Scan before you sample
- Same technique, same timing as a singleton
- Two ways in
- Two separate placentas: use both routes
- Fused or unclear: aim for the far edge
- Never cross one placenta to reach the other
- Chorionic villi under the microscope
- When the result is not clear
- Know the map before you plan the route
Amniocentesis in multiples
Fluid, second trimester, and proving you sampled two sacs
- Scan before you sample
- Same technique, later in pregnancy
- Why not do it earlier
- Two ways to sample two sacs
- Choosing where each needle goes in
- Colour Doppler shows the blood vessels
- Ultrasound view of fetal parts in amniotic fluid
- A spinal needle is the instrument
- The dye trick, step by step
- Reading the colour
- An ampoule of indigo carmine dye
- Never use methylene blue for this
- Warn the mother about her urine
- When no dye is available
- One puncture, two samples
- Why anyone would choose it
- How it is done
- What can go wrong
- Amniotic fluid drawn into syringes
Why the tests are ordered
Indications and where to find the contraindications
- What CVS is mostly for
- What amniocentesis is used for
- Contraindications
Outcomes and complications
What the numbers say, and what they cannot say
- The headline
- Why the loss rate is so hard to pin down
- What that means for consent
- Loss after CVS: the reported figures
- 2.0%
- Reading that comparison
- The case for testing early
- Loss after amniocentesis: the figures
- ~1%
- Identical twins: the evidence runs out
- The two studies, and they disagree
- What to do with two conflicting studies
Key points
What to carry out of this topic
- Key points: who and how
- Key points: dye and rhesus
- Key points: the numbers and their limits
References
The sources behind every claim in this topic
- References
- References (continued)
- References (continued)
- Suggested readings
- Suggested readings (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition