My baby's heart 💓

I'm working on flipped to 38 weeks, and had an appointment today. I hadn't eaten anything and only drank water for my urine sample. Today went completely different than expected and when we checked her heart she was in the 180 bpm range, normally she is in the 150 bpm range. They hooked me up and said she was very active so that was good but her heart kept skyrocketing to 200 bpm rang, the highest I saw was up to 212. They sent me to get an sonogram and they said the placenta and fluids were good so they aren't concerned and sent me home. I'm now freaking out because looking it up I think there is a possibility for her to have tachycardia. Has anyone experienced this or have any advice?