Fetal Growth Assessment in Twin Pregnancies: Evidence-Based Evaluation of Singleton Versus Twin-Specific Growth...

The epidemiology of twin pregnancies has shifted considerably over recent decades. Since 1980, the twin birth rate in the United States has increased by 76%, largely driven by the widespread use of assisted reproductive technologies (ART). This demographic change has reshaped clinical perspectives and evidence on the natural history of twin gestations, underscoring their unique risks and management needs. Twin pregnancies remain associated with a markedly higher risk of adverse outcomes compared with singletons. The perinatal mortality rate is estimated at 16.0 to 17.3 per 1000 births, with fetal growth restriction representing a major contributor. Selective fetal growth restriction (sFGR) complicates up to 10% of dichorionic and 15% of monochorionic twin pregnancies, respectively. Accurate and timely growth assessment is therefore central to surveillance strategies and clinical decision-making in these pregnancies. However, assessing growth in twins presents distinctive challenges. Physiological differences from singletons render singleton-based standards inadequate, often leading to over- or underdiagnosis of pathology. Evidence supports the use of twin-specific growth charts, particularly those stratified by chorionicity, which may improve prognostic accuracy and reduce unnecessary intervention. Additional considerations include intertwin discordance, sFGR, and evolving staging systems such as the Gratacós and modified classifications. The purpose of this review is to critically examine current approaches to fetal growth assessment in twin pregnancies. We summarize the limitations of applying singleton standards, evaluate the evidence supporting twin-specific references, and explore how chorionicity, longitudinal assessment, and Doppler studies can refine diagnosis and management. Finally, we highlight ongoing controversies, international variation in practice, and the need for further validation of diagnostic thresholds.