Yes! My boy had a SUA. He was smaller than his sister, but 100% healthy and catching up to her in weight. I was so scared for him when this was diagnosed. They decided to induce me at 36 weeks because of the SUA...I think....or a combination of the SUA and twins. Anyhow, my water broke on its own the morning I was to be induced. Again, probably more related to the twins and not the SUA but I guess there is no way of knowing.
Both my babies also had short long bones which are soft markers for DS. Again, I was terrified and worried a lot after finding this all out.
My boy had no other abnormalities detected on the u/s. In the absence of other problems, I think SUA isn't a big deal except for a smaller baby.
Try not to worry, but I know that is really hard. Congrats on your pregnancy!