Distribution of the bulk of the normal placenta. Review and classification of 800 cases by ultrasonography.

A series of 800 ultrasonographic placentographies is reviewed and categorized by the location of the main bulk of the placenta. It represents, to our knowledge, the first such study of the undisturbed placenta and demonstrates a remarkably even distribution with frequent overlapping of more than one uterine sector. A simple form of categorization is presented and the clinical implications and value of ultrasonography are underscored.