Introduction
Single intrauterine death (sIUD) in twin pregnancy has become a relatively frequent complication of twin pregnancy. The overall incidence of sIUD is estimated to be up to 2.6-6.2% of all twin pregnancies. 1-5 The surviving twin has many complications, such as brain damage, preterm birth, and survivor intrauterine death. 1, 6, 7Out of these complications, preterm birth (PTB) is a problem that can not be ignored due to its lasting adverse impact on the surviving twin. For instance, brain damage and multiple organ immaturity caused by PTB aggravate the bad prognosis in the surviving twin. 6 Because of peculiar chorionic problem in twins and vascular communication in monochorionic (MC) twins, some previous systematic reviews reported that the rate of PTB was higher in MC twins than in dichorionic (DC) twin pregnancy.2, 7, 8 However, studies about PTB related to sIUD in MC twins are limited. Therefore, the purpose of this study was to analyze PTB-related factors for sIUD in MC twins.