I just wrote you elsewhere, curious, about this type of anomaly -- something I share with you two. In my case it was uterus didelphys.
Curious, here's why no one noticed your unusual uterus while you were pregnant -- they weren't looking! They don't expect it, they don't look for it, and they zoom through those ultrasounds like it was nothing very important.
I'm so, so very sorry that you lost your baby. Kia is right that premature labor is very common in cases like ours.
Kia, I also experienced a ruptured uterus during my first pregnancy. It was the internal septum that ruptured, apparently due to the kicking from that little foot! What a disaster.
I don't agree with you, Kia, that mullerian anomalies are not necessarily associated with a host of menstrual difficulties. When any organ in the body is . . . unusual, then it is very possible that other organs and/or functions can also be out of the norm. I speak from experience, oh, believe me, years and years of experience.
The problem, as I mentioned to Curious in another post, is that most docs know very little about us, and they aren't always interested in learning new things. You must find the most experienced gyn you can so there's a hope of getting good care.