# Ultrasound Animal Challenge 4 – Answer

## Metadata
- Content type: Blog
- Canonical URL: https://123sonography.com/blog/ultrasound-animal-challenge-4-answer
- Published: October 3, 2022
- Last updated: November 10, 2022

## Overview
Get the answer to our fourth Ultrasound Animal Challenge here!

## Authors
- [Univ. Prof. Dr. Thomas Binder](/speaker/146) - Medical University of Vienna and founder/CMO 123Sonography, Webinar Moderation

## Content
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The answer to the question "[What does the 'butterfly sign' in ultrasound tell you about the fetus?](https://123sonography.com/blog/ultrasound-animal-challenge-4-butterfly-sign)" 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 "us-animal-challenge-butterfly-us.png") ](https://vimeo.com/756306266&title=0&byline=0&portrait=0)

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”:

- [Tiger-stripe Sign](https://123sonography.com/blog/ultrasound-animal-challenge-1-%E2%80%93-what-tiger-stripe-sign)
- [Snake Sign](https://123sonography.com/blog/ultrasound-animal-challenge-2-snake-sign)
- [Tail of a whale](https://123sonography.com/blog/ultrasound-animal-challenge-3-tail-of-whale)