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Radiology
Triploidy
Built from Obstetric Imaging
What’s inside
13 sections · 97 slides
Overview
- What this deck covers
What triploidy actually is
Counting chromosomes before naming anything
- How many chromosomes a normal cell carries
- Words for extra chromosome sets
- So what is triploidy?
- Karyotype with three of every chromosome
- What triploidy does to a pregnancy
How common it is
Common at conception, almost never at birth
- 1%-3%
- Where it sits among causes of miscarriage
- How often it is still there later on
- Survival, and the rare mosaic cases
- Maternal age does not change the risk
Where the extra set comes from
Three different accidents, one result
- The normal arithmetic of fertilisation
- Three routes to 69 chromosomes
- Naming the two origins
- 60%
- An argument that ran for years
- The study that anchored the paternal view
- How gestational age settles the argument
Two very different pictures
The same 69 chromosomes, opposite appearances
- Why the parent of origin changes the appearance
- Type I: the father's extra set
- Type II: the mother's extra set
- The two phenotypes side by side
- Read the comparison chart like this
- Comparison of Paternal and Maternal Origins of Triploidy
- The printed comparison chart
- Which type miscarries earlier
- Severe morning sickness as a clue
What the mother goes through
Triploidy is not only a fetal problem
- Complications reported in a 10-year series
- Newer figures split by origin
Triploidy and the partial mole
Overlapping, but not the same thing
- Why the two must be told apart
- How the two overlap
- What the pathologist looks for
- One swollen villus does not make a mole
- Paternal cases carry the molar risk
- Swollen placental villi under the microscope
What you see on ultrasound
The main way triploidy is found before delivery
- Ultrasound is the main tool
- When to think of triploidy
- First-trimester clues
- Reading the first-trimester scan
- Small fetus with head-to-body disproportion at 11 weeks
- Thin non-cystic placenta beside the sac
- Early scan of a fetus with 69,XXX
- A large cohort backs the pattern up
- Placenta studded with small dark spaces
- The second-trimester scan
- Head and abdomen measured weeks apart
- Enlarged fluid spaces inside the fetal brain
- Fluid collection behind the cerebellum
- Abnormal fetal kidney on the scan
- Four findings in one triploid fetus at 16 weeks
- What a 25-case series found
- The same series, outside the head
- Before the checklist
- Ultrasound Findings With Triploidy
- The printed anomaly checklist
- Does MRI help?
Screening blood tests and cell-free DNA
Helpful, but never a reliable net for triploidy
- First-trimester combined screening
- How far the markers move
- The markers point in opposite directions
- A screening result that names the wrong condition
- What cell-free DNA screening is
- Why triploidy slips through
- Evidence on how often it is missed
- Two different fingerprints on cell-free DNA
- An extra haplotype usually is not triploidy
- Making low fetal fraction work for you
- Counselling on a suspicious result
What else can look like this
Differential diagnosis from the imaging findings
- Other causes to consider - part one
- Other causes to consider - part two
- What they all share
Confirming it and managing the pregnancy
From suspicion to a definite answer
- From suspicion to diagnosis
- Invasive testing
- Getting the answer quickly
- Telling paternal from maternal in the laboratory
- Scanning again soon
- Counselling and the options
- If the pregnancy continues
After the pregnancy ends
Pathology, hormone surveillance and future pregnancies
- Send everything to pathology
- The case for testing every specimen
- Hormone surveillance after a confirmed mole
- A wider net for paternal cases
- Contraception during follow-up
- When the hormone stays high
- The next pregnancy
Take it home
The signs, the referral, the key points
- Classic signs
- What the referring physician needs to know
- Key points - the genetics
- Key points - the imaging
- References
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- Suggested reading
- Suggested reading (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition