One of the uteri contains the pregnancy, the other only decidua. If only the latter is evacuated the pregnancy will normally develop. If only the pregnant uterus is evacuated the decidua will be shed spontaneously, which will take several days. It is highly unlikely that both uteri are pregnant since this requires simultaneous ovulation in both ovaries. It may be possible after hormonal treatment to stimulate ovulation in case of infertility.
Complete duplication including the vagina is rare.
We have seen very few. Generally one of the vaginae is in use, the other is hardly detected since the septum lies snugly against the wall. If the open vagina is entered almost always the pregnant uterus will be entered and the pregnancy interrupted. But the other uterus contains decidua which will be shed during the following days. A seventeen year old girl came for termination of her unwanted pregnancy.