Fetal imaging
From imaging to clinical diagnosis
The fetal thyroid
From the 20th week of pregnancy, it is possible to obtain ultrasound images of the fetal thyroid.
Indications of obstetric ultrasound of thyroid
- In patients with Basedow treated with synthetic antithyroids.
- In patients with Basedow and TSH antireceptors (TRAK+).
- In patients who have combined the previous two criteria.
- In patients who have been treated with their Basedow (surgery or radioactive iodine) with TRAK+.
There are no other indications (except research work), especially not hypothyroidises with anti-TPO + antibody (= Hashimoto thyroidism).
When to do this ultrasound?
• Fetal thyroid measurement
- From 20-22 SA.
- In case of treatment with PTU > 1cp and/or TRAK +.
Echographic follow-up is required every month.
• Search for points of Borgard, Todt and superior humeral
- From 25 SA if TRAK+ (risk of hyperthyroid) Bone maturation advance).
- From 32SA if treatment with synthetic antithyroid only (risk of fetal hypothyroidism).
• Study of fetal mobility
Hyperactivity of hypothyroid.
• Measuring fetal heart rate
Systematic but rarely modified.
• Study of the thyroid in 13 cm/s Color Doppler
Only in the case of goiter, in the total absence of any fetal movement.
How do I get the right cuts ?
At the neck level, be well orthogonal to the spine with:
- a symmetrical vertebra (V),
- a forward trachea, easy to spot.
Then adjust the cutting plane in height to visualize the typical C cricoid (anechogenic line behind the ellipse shape trachea).
Scarcely go down: as soon as it disappears, the trachea becomes "round"... it's the thyroid.
Measures
- Normal thyroid does not exceed vertebral diameterIf volume increases.
In case of increase a follow-up will be done on a curve every 15 days.
The curves
- Curve of D.Luton and E. Vuillard (diameter and perimeter).
- Ranzini Curve (perimeter only).
Normal bone maturing
- Point of Bécard visible from 31-32SA.
- Point of Todt visible from 35-36SA
Doppler Study
- Only in case of goiter.
- Risk of false positive of global hypervascularization due to the constant movements of the throat of the hypothyroid.
So to interpret:
- in the absence of movements,
- and with the general mother-fetal context.
Hypothyroidism = peripheral flash
aloneHypothyroidism = flash total
diam 5th Vuillard
perim 5th Vuillard
Fetal thyroid curve.
22 SA High frequency probe.
Goiter 28 SA.
Goiter 28 SA.
Moderate goiter 32 SA.
Goiter 26 SA.
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