Repeat ultrasound?

So my doctors office just called and said that in 10-14 days they want me to get a repeat ultrasound.my first ultrasound was at 6w3d and they didn't say anything was wrong but they just want to make sure everything is looking good . With my first pregnancy my daughter I had one at 6w6d and then not another till 13w1d .Is this normal and did this happen to you ? I was able to see the heartbeat (116) and they didn't say that had to do with anything.