Baby's HeartRate question..Plss help!!

My baby's HR has been around 160s since around 9/10 weeks up until now (15 weeks). This morning in my OB visit, HR was 154. My Dr seem to be not worried about it and he says that it's normal as the baby size grows. I still cannot get it out of my head and was hoping that the moms here can help me with their inputs. Did any one notice this with their baby during this or a previous pregnancy??