Figure 7. Classification criteria for US differentiation of septate from bicornuate uteri. A, When apex (3) of the fundal external contour occurs below a straight line between the tubal ostia (1, 2) or, B, 5 mm (arrow) above it, the uterus is bicornuate. C, When apex is more than 5 mm (arrow) above the line, uterus is septate.