INTRODUCTION: Predicting preterm delivery in twin gestations helps identify women who may benefit from interventions such as antenatal corticosteroids within 7 days of delivery. Our aim was to quantify the performance of short cervical length (CL) (<25mm) in outpatient twin gestations to predict delivery within 7 days. METHODS: Outpatient transvaginal ultrasound reports for diamniotic twin gestations of 23w 0d to 28w 6sd were reviewed between January 2010-July 2014. Index CL was defined as the first CL less than 25mm. Primary outcome was the positive predictive value (PPV) of spontaneous delivery within 7 days of index CL. Secondary outcomes included PPV of index CL of 15mm and 10mm. RESULTS: Of the 411 included charts, 52 patients (12.6%) had a short cervix. There were no significant differences in major risk factors for preterm birth. Four women (1% of the total study population) delivered within 7 days of index CL; three of these had a short cervix while one had a normal CL. PPV of 25mm CL was 5.8% (95% CI 1.2-16.0); NPV 99.7% (95% CI 98.5- >99.9). The PPV of 15mm and 10mm CL were 9.1% (95% CI 1.1-29.2) and 20.0% (95% CI 7.5-55.6). CONCLUSION: In this retrospective observational study, CL of less than 25mm had a poor positive predictive value for delivery within 7 days. 25mm CL cutoff may not be useful to time interventions such as betamethasone administration or hospitalization. PPV increases with decreasing CL. Other tools can be considered in addition to CL measurement for intervention.