| Uterine cavity shape | External contour |
---|---|---|
Class U0: normal uterus | Straight, curved interostial line or internal indentation < 50% myometrial thickness | Normal outline or external cleft < 50% of uterine wall thickness |
Class U1: dysmorphic uterus | Abnormal | Normal outline or external cleft < 50% of uterine wall thickness |
 a. T-shaped | Narrow cavity; thickened lateral walls; correlation of two-third uterine corpus and one-third cervix |  |
 b. Infantilis | Narrow cavity without wall thickening; correlation of one-third uterine body and two-third cervix |  |
 c. Others | Internal indentation < 50% myometrial thickness |  |
Class U2: septate uterus | Internal indentation > 50% myometrial thickness | Normal outline or external cleft < 50% of uterine wall thickness |
 a. Partial | a. Division above of the internal cervical os |  |
 b. Complete | b. Division up to the internal cervical os |  |
Class U3: bicorporeal uterus |  | External cleft > 50% myometrial thickness |
 a. Partial | Division above of the internal cervical os | Division above the cervix |
 b. Complete | Division up to the internal cervical os | Division up to the cervix |
 c. Bicorporeal septate | Midline fundal indentation (myometrial thickness at the central point of the external cleft) > 150% uterine wall thickness (average myometrial thickness |  |
Class U4: hemi-uterus | Unilateral formed cavity | Unilateral formed corpus |
 a. With a rudimentary (functional) cavity | With communicating or non-communicating functional contralateral horn of cavity |  |
 b. Without rudimentary (functional) cavity | Without functional contralateral horn of cavity |  |
Class U5: aplastic uterus | Â | Â |
 a. With rudimentary (functional) cavity | Cavity remnant/s present | Cavity remnant/s present |
 b. Without rudimentary (functional) cavity | Cavity remnants absent | Full uterine aplasia or uterine remnants present |
Class U6: unclassified cases | Â | Infrequent anomalies, subtle changes, or combined anomalies |