Anyone have this happen with their baby?? (Heart issue)

I came to labor and delivery for decreased fetal movement, I’m 28 weeks and 2 days. Every 20 minutes or so, her heartrate jumps dramatically, usually to around 218bpm, stays like that for a couple minutes, then drops again. The hospital is keeping me overnight for further monitoring, but the wait to know if something is seriously wrong is torture!! Anyone else have/know about something similar?