STOPPIT-2 is a multicentre open label randomised controlled trial of the Arabin pessary (CE marked Device) versus Standard treatment in women with twin pregnancy. The study is in two phases - a SCREENING phase, in which women with a short cervix (cervical length of ( less or equal to 35mm) will be identified, and a TREATMENT phase, in which women with a short cervix will be randomised to treatment with Arabin pessary or Standard treatment. Women will be seen in the antenatal clinic setting.