placenta abruption!?!

I had a pretty bad fall this morning, I went to the hospital, and l&d watched me for 4 hours to make sure I wasn't having any contraction it any bleeding. They did a ultrasound, baby looks great. But Dr says I'm at risk for placenta abruption. I'm only 28 weeks, I was already a high risk for preterm labor. Has anyone had a bad fall but go on to having a full term labor with no complications?