What is the definition or description of: baby arches back?

Sandifer Sign: It's called sandifer sign. It tend to suggest a child has reflux. Please talk to your doctor to help with reflux. While we used to give a lot of medication for gerd, there are many non-pharmaceutical way to help you child.

Need more info: There can be several reasons for babies arching their back. It can be an idiosyncrasy (habit), it can indicate reflux, but it could also indicate a neurologic issue like seizures, or increased muscle tone. Normally seizures would also involve change in mental status or eye movements. If you take short videos of the episodes then you can share them with your pediatrician.