Fig. 1

a T2-weighted magnetic resonance imaging (MRI): red arrowhead indicates the cesarean scar defect. b T2-weighted MRI: the appearance of the cavity (red arrow) is suspicious for a bicornuate uterus. c Hysterosalpingography: the right fallopian tube is not connected to the small cavity (red arrow), ruling out a bicornuate uterus. d Schematic of the patient's uterus. (a: The cesarean scar defect, b: The small cavity) (e-g) Hysteroscopic images. e Polyps (yellow arrowheads) around the cesarean scar defect (corresponding to “a” on schematic). f The entrance (yellow arrow) of a small cavity viewed from the cesarean scar defect (corresponding to “h” on schematic). g The inside wall of the small cavity (corresponding to “i” on schematic). The wall of the cavity is smooth and hard, with no endometrial tissue present