Objective: The purpose of this study was to develop a predictive model for cesarean delivery after induction of labor (IOL) in twin pregnancy. Design: Retrospective cohort study Setting: University hospital. Population: Twin pregnancy who underwent IOL from 2005 to 2018 Methods: The study population was randomly divided into the training and test sets at a ratio of 2:1. Three-fold cross-validation (CV) with 100 times repetitions was applied to select the best model. Main outcome measure to develop and validate a prediction model for cesarean delivery after IOL in twin pregnancies. Results: A total of 1,703 twin pregnancies were analyzed, including 1,356 women in the development cohort of the SNUH database and 347 women in the external validation cohort of the SNUBH database. In the development cohort, the clinical variables that were different between the successful and failed IOL groups were included in the logistic regression analysis, and the final prediction model, composed of five variables (maternal age, maternal height, parity, cervical effacement, and summated birth weight of both twins), was selected with an AUROC of 0.742 (95% confidence interval [CI], 0.700-0.785) and 0.733 (95% CI, 0.671-0.794) in the training set and test set, respectively. A nomogram for predicting the risk of cesarean delivery after IOL in twin pregnancies was also developed. Conclusion: A prediction model to provide information and evaluate the risk of cesarean delivery after IOL in twin pregnancies was developed. Keywords Twin pregnancy, induction of labor, cesarean section, prediction model

Objective: To compare maternal, perinatal and long-term outcome of triplet pregnancies managed expectantly with those reduced to twins Design: A retrospective cohort study Setting: Tertiary medical institutions in South Korea Population: We examined short-term and long-term outcomes in 524 triplet pregnancies with three live fetuses before 14 weeks of gestation that were comprised of expectant management(EM) group (n=213) and embryo reduction(ER) group (n=311) from 2006 to 2017. Methods: The two groups were compared for the following outcomes. Main Outcome Measures: 1) the rates of non-viable pregnancy loss before 23 weeks, 2) the rates of preterm birth before 32 weeks of gestation; 3) the number of survival fetuses; and 4) long term neurodevelopmental outcomes. Results: In the EM group, the risk of preterm delivery (<36, <34, <32, and <28 weeks) was higher compared to the ER group. However, the risk of non-viable pregnancy loss was lower [2(0.9%) vs. 20(6.4%), p=0.008] in EM group, and the rate of cases with at least one alive neonate were higher in EM group than ER group [208(97.7%) vs. 287(92.3), p=0.013]. The survival rate until discharge of neonates were also significantly higher in the EM group than the ER group [607(95.0%) vs. 545(87.6), p=0.001]. The risk of developmental delay or cerebral palsy in survived neonates was not different between the two groups of cases. Conclusions: In triplet pregnancies, EM may improve the chance of fetal survival, without any significant differences in developmental delay and cerebral palsy.