 Twins As an independent marker of fetal aneuploidy, nuchal translucency is particularly useful in twins because of the inability of maternal serum markers or age to identify the fetus at risk. Nuchal translucency measurement allows each fetus of a twin pregnancy to be assessed individually; the distribution of measurements does not differ significantly between singletons and twins so that standard thresholds can be used [9,10]. In dichorionic twins, fetus-specific risks are calculated on the assumption each twin has an independent risk reflected by its own nuchal translucency [2,11,12]. In monochorionic twins, a pregnancy-specific risk is calculated using the average nuchal translucency thickness of both fetuses [2,13]. As in singletons, increased nuchal translucency may also be a marker of fetal structural anomalies, genetic syndromes, and intrauterine demise in twins. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Nuchal Translucency Evaluation Special Imaging Considerations Measurement of the nuchal translucency has been standardized in order to improve its performance in screening for fetal aneuploidy. Quality assurance programs for nuchal translucency assessment have been established by the Fetal Medicine Foundation in London and the Nuchal Translucency Quality Review in the United States.
Nuchal Translucency Evaluation at 11 to 14 Weeks Gestational Age.  Twins As an independent marker of fetal aneuploidy, nuchal translucency is particularly useful in twins because of the inability of maternal serum markers or age to identify the fetus at risk. Nuchal translucency measurement allows each fetus of a twin pregnancy to be assessed individually; the distribution of measurements does not differ significantly between singletons and twins so that standard thresholds can be used [9,10]. In dichorionic twins, fetus-specific risks are calculated on the assumption each twin has an independent risk reflected by its own nuchal translucency [2,11,12]. In monochorionic twins, a pregnancy-specific risk is calculated using the average nuchal translucency thickness of both fetuses [2,13]. As in singletons, increased nuchal translucency may also be a marker of fetal structural anomalies, genetic syndromes, and intrauterine demise in twins. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Nuchal Translucency Evaluation Special Imaging Considerations Measurement of the nuchal translucency has been standardized in order to improve its performance in screening for fetal aneuploidy. Quality assurance programs for nuchal translucency assessment have been established by the Fetal Medicine Foundation in London and the Nuchal Translucency Quality Review in the United States.