Abstract
Importance Monochorionic (MC) twins are hemodynamically connected by vascular anastomoses within the single shared placenta. The transfer of fluid or blood from one fetus to the other may result in development of pathologic complications, such as twin-twin transfusion syndrome, twin anemia polycythemia sequence, selective intrauterine growth restriction, and twin reversed arterial perfusion sequence. Monoamniotic gestations, which comprise a small fraction of MC pregnancies, can also present with unique challenges, particularly antepartum umbilical cord entanglement. All these complications carry a high risk of fetal morbidity and mortality if not recognized and managed in a timely fashion. Objective The purpose of this article is to review evidence-based management of complicated MC twin gestations and propose a standardized approach to surveillance. Evidence Acquisition Monochorionic gestations account for the majority of complications that occur in twin pregnancies; however, there is unclear evidence on the appropriate surveillance for and management of specific complications associated with these pregnancies. Results This article summarizes management for each specific type of MC complication in a structured and clear manner. Conclusions Early pregnancy ultrasound, ideally between 10 and 13 weeks' gestation, is critical for the diagnosis and characterization of twin pregnancies. To improve outcomes for MC twins, appropriate fetal surveillance should be initiated at 16 weeks' gestation and continued until delivery. Relevance Improve perinatal outcomes in MC twin pregnancies. Target Audience Obstetricians and gynecologists, family physicians Learning Objectives After completing this activity, the learner should be better able to describe the sonographic findings used to establish the diagnosis of MC twin pregnancies; identify complications unique to MC twins pregnancies, including twin-twin transfusion syndrome, twin reversed arterial perfusion sequence, twin anemia polycythemia syndrome, co-twin demise, cord entanglement, and conjoined twins; and explain the management of complications associated with MC twin pregnancies. © Wolters Kluwer Health, Inc. All rights reserved.