Diagrams of the ASRM definitions of normal/arcuate, septate, and bicornuate uterus 4.
Normal/arcuate: depth from the interstitial line to the apex of the indentation <1 cm and angle of the indentation >90 degrees.
Septate: depth from the interstitial line to the apex of the indentation >1.5 cm and angle of the indentation <90 degrees.
Bicornuate: external fundal indentation >1 cm. Internal endometrial cavity is similar to a partial septate uterus.