Intrauterine death of one fetus in monochorionic twins [Expert opinion or recommendation] When intrauterine death of one fetus in monochorionic twins is detected, referral to a regional prenatal diagnostic center or fetal medicine center for detailed evaluation is recommended (recommendation level B). Question 1: Etiology of intrauterine death in monochorionic twins [Expert opinion or recommendation] The most common causes of intrauterine death in monochorionic twins are fetal chromosomal abnormalities, structural developmental abnormalities, TTTS, TAPS, severe sIUGR, and single amniotic sac twin umbilical cord entanglement (Level of evidence IIb). Question 2: How to consult the prognosis of the surviving fetus after intrauterine death of a monochorionic twin fetus? [Expert opinion or recommendation] Due to the unique nature of monochorionic twins, it is recommended that the prognosis of the surviving fetus be consulted by an experienced specialist (level of recommendation A). After the death of one fetus in monochorionic twin fetuses, blood from the surviving fetus is backed up to the stillborn fetus due to interplacental vascular anastomosis, thus causing acute or prolonged hypotension and hypoperfusion levels, which may lead to death of the other fetus, and may also cause ischemic injury to the surviving fetus’ organs, especially the nervous system. In 2011, a meta-analysis of perinatal outcomes after the death of one fetus in 22 studies of twins found that the risk of simultaneous death of the other fetus after the death of one fetus in monochorionic twins was significantly higher than that in bichorionic twins (15% and 3%, respectively); however, there was no significant difference in the incidence of preterm birth compared with bichorionic twins (68% and 54%, respectively); and in postpartum neurological imaging abnormalities were detected (34%, 16%, respectively); and there was a significant difference in neurological developmental abnormalities in surviving fetuses (26%, 2%, respectively) 37] (Level of evidence Ia). Question 3: How to manage the pregnancy after the occurrence of one fetal death in monochorionic twins? [Expert opinion or recommendation] It is recommended that prenatal diagnostic centers or fetal medicine centers develop individualized management plans for pregnant women with first trimester death in monochorionic twins (recommendation level B). The need for immediate delivery of the other surviving fetus after intrauterine death of one of the monochorionic twins is controversial, and there is no strong evidence to guide the conclusion so far. It has been argued that immediate delivery does not improve the prognosis of the surviving fetus on the grounds that neurological damage occurs as a result of a momentary intrauterine “acute transfusion” of the other fetus at the time of death of one fetus, and that immediate delivery does not improve the neurological damage that has already occurred in the surviving fetus but may increase the incidence of preterm delivery unless Severe abnormalities in fetal heart monitoring or severe anemia in the surviving fetus in late pregnancy are detected. In the surviving fetus, the presence of severe anemia can be determined by ultrasound detection of the peak systolic flow velocity (PSV) in the middle cerebral artery of the fetus. If severe anemia is present, intrauterine transfusion of anemic fetuses can be used to correct the anemia, prolong the gestational weeks, and reduce the risk of neurological injury in surviving fetuses, but is controversial. A cranial MRI scan of the surviving fetus 3 to 4 weeks after the occurrence of intrauterine fetal death may detect some severe fetal cranial injuries earlier than ultrasonography. If imaging reveals neurological lesions in the surviving fetus, the prognosis of the fetus needs to be discussed in detail with the family [38]. The management of pregnancy in pregnant women focuses on monitoring pregnancy-related complications and comorbidities. Some evidence-based medical evidence suggests that the incidence of maternal hypertension-related disease in pregnancy is increased after intrauterine death of one fetus in twin pregnancies, requiring blood pressure monitoring and urine protein screening, and that the risk of DIC is theoretically present but rare in clinical reports. The risk of maternal infection is not increased after the death of one fetus in a monochorionic twin pregnancy.