I am so very sorry. Like adgal says, I can't begin to imagine what it must be like to have to deal with something like that.
However, I think you should be okay with another baby if you make sure your doctor monitors you carefully. I am no doctor and I don't really know how this works but I know a lady who had the same problem. But they saw it on the ultrasound and so the doctor kept a close eye on it and he ended up doing a c-section for her 4 weeks before her due date because he started to get worried.
I know that you are not the only one to lose a baby for this reason. I don't know why. I don't know if it can't always be seen on an ultrasound or if maybe even if you see it, you can't always tell if it's going to be serious or not.
Maybe you should ask your doctor what happens if this happens again. Ask if they can monitor you more closely to see if it is happening. And ask what they can do if it does happen. If they CAN tell if it's happening and there IS something safe they can do to prevent it from being a problem, then you don't have to worry.
Oh my gosh. I am so very sorry, I cannot even imagine what you must be going through. I don't pretend to know a lot about this or how it may have been prevented. But, based on what I have read this sounds like one of those horrible accidents that will not be repeated. I am sure the chances of something like this happening again would be almost nil. I am so sorry, and I am sending all my love and support your way. Amanda