Baby heart rate lower 39 weeks

Miranda

My babys HR has been 150s throughout my entire pregnancy, even at my 38 wk appointment was still 150s. Just had my 39+4 appointment and it was 120. Dr seemed to think it was fine and normal but scares me. Did this happen to anyone else? If so- Did labor start soon after?

I’ve had no signs, no mucus plug, no leaking, no bloody show, no contractions, no braxton hicks.... nothing.