The speculum was removed and a 5 MHz transvaginal 3D ultrasound probe inserted into the vagina (Voluson 730; KretzTechnik, Austria).
• three-dimensional saline infusion sonohysterography (3D SIS) was performed in all cases. A sterile Cuscoe speculum was passed, the cervix visualized and cleaned with sterile chlorhexidine solution. A 3.3 mm soft plastic paediatric naso-gastric suction catheter was then passed through the cervix into the uterine cavity without grasping the cervix.