We first heard heart rate on Doppler at office on Monday and was 172-174. On Wednesday I had elective ultrasound but not a medical one so no measurements to determine gestational age and heart rate was 163. Per lmp I would be 10w4d for Doppler and 10w6d for ultrasound but think I ovulated later so closer to 10w0d. Is it normal for heart rate to be 10bpm lower in a 2 day period?