Heart rate over 200bmp at 36 weeks

So I’m 36 weeks tomorrow and today at my biophysical my baby’s heart rate was going over 200bmp, doctor said it was okay because it ended up going down but I’m still very concerned. The highest her heart rate ever was was 176bpm at 10 weeks, it’s been between 145-155bmp ever since even when active, but today it was in the 170’s-190’s and over 200 at times. She passed all her tests on the ultrasound afterwards though. Has anyone else seen this happen?