Uterine didelphys is a Class III Mullerian duct anomaly with complete non-fusion producing two separate uteri and cervices. Recognized associations include recurrent abortion, premature labor, malpresentation (transverse lie), infertility, and ipsilateral renal agenesis. Endometriosis arises from retrograde menstruation or coelomic metaplasia and is an independent pathological process not caused by uterine didelphys. Therefore endometriosis is the exception in the list of complications. \[\boxed{\text{Endometriosis (Option B)}}\]