A device for intrauterine insertion which comprises: - an expandable balloon having a proximal end and a distal end, sized to fill the uterine cavity during expansion and to exert pressure against its boundary wall on substantially the total surface of said wall; - a catheter having a proximal end and a distal end, where said distal end of said catheter is connected with the proximal end of said balloon, and said proximal end of said catheter is connected to a source of fluid and means for supplying pressurized fluid to the balloon through said catheter to effect and maintain its expanded condition, wherein said catheter is connected with a seal connector to said balloon, characterized in that said seal connector comprises: - a first perforated body and a second perforated body, mounted axially, i.e. along the axis; - two elastic bands, and (83") axially housed inside said first and second perforated bodies and, where a first elastic is mounted on supports and comprised, respectively, on said second and on said first perforated body and a second elastic (83") is mounted on supports and present, respectively, on said second and on said first perforated body; where said first and said second perforated body receive, respectively, a first toothed wheel capable of radially deforming and a second rigid toothed wheel, where said first and second toothed wheel and engage between them so as to form a ratchet, that is a mechanical device that allows a rotary movement around the axis in one direction only. - an expandable balloon having a proximal end and a distal end, sized to fill the uterine cavity during expansion and to exert pressure against its boundary wall on substantially the total surface of said wall; - a catheter having a proximal end and a distal end, where said distal end of said catheter is connected with the proximal end of said balloon, and said proximal end of said catheter is connected to a source of fluid and means for supplying pressurized fluid to the balloon through said catheter to effect and maintain its expanded condition, wherein said catheter is connected with a seal connector to said balloon, characterized in that said seal connector comprises: - a first perforated body and a second perforated body, mounted axially, i.e. along the axis; - two elastic bands, and (83") axially housed inside said first and second perforated bodies and, where a first elastic is mounted on supports and comprised, respectively, on said second and on said first perforated body and a second elastic (83") is mounted on supports and present, respectively, on said second and on said first perforated body; - a first perforated body and a second perforated body, mounted axially, i.e. along the axis; - two elastic bands, and (83") axially housed inside said first and second perforated bodies and, where a first elastic is mounted on supports and comprised, respectively, on said second and on said first perforated body and a second elastic (83") is mounted on supports and present, respectively, on said second and on said first perforated body; where said first and said second perforated body receive, respectively, a first toothed wheel capable of radially deforming and a second rigid toothed wheel, where said first and second toothed wheel and engage between them so as to form a ratchet, that is a mechanical device that allows a rotary movement around the axis in one direction only.