8 week heart rate? FTM

Lene • Wife❤️ baby girl 💕

Last week I went in for my first sonogram at 8 weeks and baby had a strong heart rate of 171. The next day I experienced some intense abdominal pain and went to the ER just to be safe. They did another ultrasound and said baby’s heart rate was in the 140’s. Is it normal for the baby’s heart rate to fluctuate like this? Or could it just have been lower due to the amount of pain I was in? Thoughts?