Since you have a history of this problem plus additional scarring since your last pregnancy, chances are pretty high that you will experience this again.
One poster on another site mentioned that she was diagnosed with this at eight weeks but there is no way to know how soon your doctor/ ultrasound tech will be able to detect a problem.
One article I read said that this can be detected with 100% accuracy by using a combination of ultrasound and MRI.
Here is a link to a very informative article:
http://mediwire.sma.org/main/Default.aspx?
P=Content&ArticleID=139429
Congrats on your pregnancy. I hope you have a healthy pregnancy, easy delivery, and quick recovery.