Objective To determine whether second-trimester cervical length (CL) in women with a twin pregnancy is associated with the risk of emergency Cesarean section. Methods This was a secondary analysis of two randomized trials conducted in 57 hospitals in The Netherlands. We assessed the univariable association between risk indicators, including second-trimester CL in quartiles, and emergency Cesarean delivery using a logistic regression model. For multivariable analysis, we assessed whether adjustment for other risk indicators altered the associations found in univariable (unadjusted) analysis. Separate analyses were performed for suspected fetal distress and failure to progress in labor as indications for Cesarean section. Results In total, 311 women with a twin pregnancy attempted vaginal delivery after 34weeks' gestation. Emergency Cesarean delivery was performed in 111 (36%) women, of which 67 (60%) were performed owing to arrest of labor. There was no relationship between second-trimester CL and Cesarean delivery (adjusted odds ratio (aOR): 0.97 for CL 26th-50th percentiles; 0.71 for CL 51st-75th percentiles; and 0.92 for CL> 75th percentile, using CL <= 25th percentile as reference). In multivariable analysis, the only variables associated with emergency Cesarean delivery were maternal age (aOR, 1.07 (95% CI, 1.00-1.13)), body mass index (BMI) (aOR, 3.99 (95% CI, 1.07-14.9) for BMI 20-23 kg/m(2); 5.04 (95% CI, 1.34-19.03) for BMI 24-28 kg/m(2); and 3.1 (95% CI, 0.65-14.78) for BMI> 28 kg/m(2)) and induction of labor (aOR, 1.92 (95% CI, 1.05-3.5)). Conclusion In nulliparous women with a twin pregnancy, second-trimester CL is not associated with risk of emergency Cesarean delivery. Copyright (C) 2014 ISUOG. Published by John Wiley & Sons Ltd.