When Does the Brain Stem Normally Form?

Jane Foley's picture


Dear Ms. Ultrasound,
I had an ultrasound this week. I thought I was twenty weeks but measured 17 weeks 5 days. They could not find the lower part of the brain stem.

Should I be concerned? When does this normally form? At how many weeks? I have a appointment with a perinatologist in 3 weeks?


I am going to guess that they could not find what is called the cerebellum on the ultrasound. This is a part of the brain that is routinely measured on an ultrasound in the second trimester. If this was the only part of the babies anatomy that was abnormal or missing, I would not worry too much yet. Usually there are other problems found in the baby if there is a missing part of the anatomy. It seems in your case that the only issue was the cerebellum measurement.

There are a few reasons that this may not have been easily measured, from technical to a large maternal body type to operator inexperience to a real problem.

Soooooooo, take a deep breath and try and relax for now. I believe that a limited amount of stress from Mommy helps the baby and it's development. Once you have your next ultrasound, let me know what they find and we can discuss the findings.

With Regards,
-- Jane RDMS