Baby measuring one day behind

Hi girls,

So I had an ultrasound on October 17th and the baby measured at 6 weeks and 4 days with a HR of 142. I then had a repeat ultrasound on October 23rd where the baby should be measuring at 7 weeks and 3 days but it measured at 7 weeks and 2 days with a heart rate of 169. Should I be concerned about it measuring behind one day? I see my doctor on Tuesday so I will talk to her then, but in the mean time I am a little worried about....