In order to better understand uterine anomalies, we must first consider the process by which the uterus is formed. The structures which give rise to the uterus are a pair of tubes called the mullerian ducts. They remain separated at a distance throughout development. The other end of these tubes which are closest to the embryo's bottom lie side by side, close together. They will form the uterus by fusing together to become one structure.
Fusion occurs between the two middle walls which face one another.
However, the fully developed uterus is wider at top than the bottom. The next step in the development of the uterus is the widening of the top of this uterine tube. This is achieved by an expansion of the top part of the 'central wall'. This process occurs in an embryo ten to thirteen weeks old. During this stage, changes also occur in the lower aspect of the fused mullerian ducts.