Predicting outcomes in selective fetal growth restriction of monoChOrioNic Twins: an inteRnAtional observational cohort STudy protocol (CONTRAST study)

INTRODUCTION: Selective fetal growth restriction (sFGR) is a major cause of perinatal morbidity and mortality in monochorionic diamniotic (MCDA) twin pregnancies. Current management relies on umbilical artery Doppler patterns in the smaller twin. These patterns are, however, inconsistent and do not represent a reliable severity scale, complicating clinical decision-making and parental counselling. This study aims to improve risk stratification by identifying predictors of adverse outcomes, while also evaluating the pathophysiology and multi-organ impact of sFGR in early childhood. METHODS AND ANALYSIS: This is a prospective, international, multicentre cohort study conducted in six tertiary fetal medicine centres with expertise in complicated twin pregnancies. Recruitment began in March 2023 and will continue until December 2026, targeting 274 MCDA twin pairs with complete follow-up to develop a prediction model for adverse perinatal outcomes in sFGR at the time of diagnosis. Standardised data collection includes serial ultrasound examinations, advanced fetal imaging (cardiac, cerebral and 3D volumetric), fetal brain MRI and detailed placental phenotyping. Maternal and parental well-being are assessed during pregnancy and after birth. Neurodevelopmental outcome is evaluated up to 2 years after birth using validated tools. The statistical analysis plan includes predictive modelling with internal validation. ETHICS AND DISSEMINATION: The study has been approved by the ethical review boards of all participating centres. Findings will be disseminated through peer-reviewed publications, international conferences and engagement with clinical guideline committees. TRIAL REGISTRATION NUMBER: NCT05952583.