My OB cancelled the rest of my ultrasounds?

I'm 28 weeks pregnant today and I had at least 4 more sonogram appointments already made up until I give birth. I had more sonograms than usual because they found a something concerning on one of my ultrasounds before (an echogenic intracardiac focus on my baby's heart- soft marker for Down syndrome or congenital heart defects). After my blood test for chromosomal abnormalities came back negative (97% accurate) my OB decided it was safe to cancel the rest of my sonograms. I'm only 28 weeks pregnant! My last sonogram was around 26 weeks. So I won't have anymore ultrasounds at all at this point. Is it weird to not have any more sonograms now? Especially since they've found something concerning on my ultrasounds before. I always see ultrasound pictures on here from 30-35 weeks. Please advise!