Ultrasound?

K
So far with this pregnancy I have had three appointments. The first two appointments I had ultrasounds to make sure that the baby was developing okay. My last pregnancy ended in a miscarriage and they were wanting to take extra precautions. My last ultrasound was at a little over 7 weeks. Since then another ultrasound has not been brought up. I will be 15 weeks at my next appointment and I have been reading that they usually do an ultrasound around 11-12 weeks to check for down syndrome. Should I call before my appointment to see if they are planning on doing another ultrasound or can I request that they do one? How frequently did you all have ultrasounds? My next appointment is one of the few that my husband can actually make and the only one that my stepdaughter will be able to go to. I'm dying to check in on my little baby!