Optimal diagnostic management and underlying pathophysiological mechanisms of selective fetal growth restriction (sFGR) in monochorionic diamniotic (MCDA) twin pregnancies have not been fully clarified. The current diagnostic classification system based on three different umbilical artery flow patterns has no increasing scale of severity and the predictive value is limited. Since there is no treatment available for sFGR, predicting fetal deterioration is key in preventing single or double fetal demise. Outcome prediction is furthermore important in the selection of cases that will be offered selective reduction (to provide the larger twin with better prospects), as well as determining monitor frequency and possible hospital admission. As outcome prediction is clinically challenging, patient counselling is too, and parents often encounter a great deal of uncertainty during the pregnancy. Furthermore, little is known about the brain development of sFGR children (both during pregnancy and after birth). Moreover, the psychological impact of an sFGR pregnancy of the future parent)s) has not been studied before. The impact of these factors should be taken into account during patient counseling, which is currently not the case. By our knowledge, this is the first international, multicenter, prospective cohort study on that will address the abovementioned questions and knowledge gaps in MCDA pregnancies complicated by selective fetal growth restriction.