Ultrasound Animal Challenge 4 – Answer
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The answer to the question "What does the 'butterfly sign' in ultrasound tell you about the fetus?" is:
B) That no holoprosencephaly is present
![](https://123sonography.com/sites/default/files/styles/video_thumbnail/public/image/images/us-animal-challenge-butterfly-us.png?itok=X3X0AwXL)
The butterfly sign on ultrasound shows the normal appearance of the choroid plexuses of the fetal brain (axial image plain). Its absence in the first trimester is a warning sign for holoprosencephaly, a developmental disorder where the brain fails to develop to hemispheres. This abnormality is frequently incompatible with life.
![Ultrasound image of brain with what looks like a butterfly with labels.](https://123sonography.com/sites/default/files/styles/article_image/public/image/images/us-animal-challenge-butterfly-label.png?itok=30NIDz8s)
Yours,
Thomas Binder and the 123sonography team
PS: If you missed the previous Animal Challenge posts you can always visit our “zoo”: