An Open Randomised Trial of the Arabin Pessary to Prevent Pre-term Birth in Twin Pregnancy

Inclusion Criteria: * Women presenting with twin pregnancy (monochorionic or dichorionic) * Women with gestation established by scan at ≤16 weeks according to NICE guidelines. * Women aged 16 years or older * Women wishing to participate in both the SCREENING and RANDOMISATION phase of the study Exclusion Criteria: * Women unable to give written informed consent * Women with known significant congenital structural or chromosomal fetal anomaly at the time of inclusion * Women with existing or planned cervical cerclage in the current pregnancy * Women who with existing or planned (prior to 20+6 weeks gestation) treatment for twin to twin transfusion syndrome in the current pregnancy * Women with suspected or proven rupture of the fetal membranes at the time of recruitment * Women with singleton pregnancy or higher order multiple pregnancies * Women with known sensitivity, contraindication or intolerance to silicone * Women involved in a clinical trial of an investigational medicinal product (CTIMP)