Synmastia can occur naturally or can be a result of breast augmentation.  It is a condition where the breast mound continues across the sternum in the midline, such that the two breasts are not fully separated from each other.  If it is due to placing the breast implants too close together at the time of augmentation, it can be corrected by re-operating and placing tucking sutures on the inner aspects of the implant pockets on both sides to restore the normal separation between the two breasts in the region of the sternum.