① Use a speculum to expose the cervix, insert the distal end of the balloon catheter into the cervix, and ensure that both balloons pass through the internal cervical orifice;
② Fill the uterine balloon with 40m saline (red filling port);
③ After filling, pull the balloon backward until the uterine balloon is close to the internal cervical orifice;
④ At this time, the guiding balloon can be seen at the external cervical orifice, fill the guiding balloon with 20 m of normal saline, take out the speculum, and then inject 20 m of normal saline;
⑤ After confirming that the balloon is placed on both sides of the cervix, fill it with normal saline (according to the injection volume of 20ml each time, gradually increase or decrease the volume of each balloon by 80ml.