ACR Appropriateness Criteria® Multiple Gestations: 2024 Update.

The incidence of twin pregnancies has been rising, largely attributable to increasing use of artificial reproductive techniques. Ultrasound plays a critical role in establishing the chorionicity and amnionicity of multiple gestations, a key predictor of the expected risk and complications, along with guiding future clinical and imaging follow-up examinations and intervals. People carrying multiple gestations will typically undergo more ultrasound examinations (and occasionally fetal MRI) than those carrying singletons, at minimum including a first trimester dating scan, nuchal translucency scan at 11 to 14 weeks, an anatomy scan at 18 to 22 weeks, and other scans in the second and third trimesters for growth and surveillance. This document clarifies the most appropriate imaging guidelines for multiple gestations for seven clinical scenarios/variants, which range from initial imaging, follow-up imaging, growth and surveillance for uncomplicated multiple gestations, and those complicated by a known abnormality or discordance between fetuses. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.