The ACR Appropriateness Criteria methodology assumes that each imaging procedures is performed and interpreted by an expert, but it should be noted that there remains considerable inter- and intra-observer variability in nuchal translucency measurements, highlighting the importance of ongoing quality assessment [14,15]. First trimester screening algorithms can be improved by assessing for the presence or absence of the nasal bone and adjusting aneuploidy risk calculations accordingly [16]. The absence of the nasal bone at 11 to 14 weeks is another powerful US marker of fetal aneuploidy; it improves the performance of early screening by decreasing the false- positive rate to 2.5% [16]. Other first trimester US markers of fetal aneuploidy such as increased frontomaxillary facial angle, an aberrant right subclavian artery, presence of tricuspid regurgitation, reversed a-wave in the ductus venosus, and increased iliac wing angle have not been incorporated into routine screening algorithms and their clinical usefulness in the general population remains uncertain [17]. The role of nuchal translucency measurement in the new era of cell-free fetal DNA screening is also uncertain. It is recommended that a first trimester US for the sole purpose of nuchal translucency screening not be performed in patients with negative cell-free fetal DNA [18]. OR Discussion of Procedures by Variant Variant 1: Routine nuchal translucency measurement at 11 to 14 weeks of gestation for single or twin gestations. Initial imaging. US Duplex Doppler Pregnant Uterus Although the utility of Doppler imaging has been investigated in research protocols, there is no literature to support a recommendation to universally incorporate Doppler studies into routine first trimester screening algorithms for fetal aneuploidy [17].
Nuchal Translucency Evaluation at 11 to 14 Weeks Gestational Age. The ACR Appropriateness Criteria methodology assumes that each imaging procedures is performed and interpreted by an expert, but it should be noted that there remains considerable inter- and intra-observer variability in nuchal translucency measurements, highlighting the importance of ongoing quality assessment [14,15]. First trimester screening algorithms can be improved by assessing for the presence or absence of the nasal bone and adjusting aneuploidy risk calculations accordingly [16]. The absence of the nasal bone at 11 to 14 weeks is another powerful US marker of fetal aneuploidy; it improves the performance of early screening by decreasing the false- positive rate to 2.5% [16]. Other first trimester US markers of fetal aneuploidy such as increased frontomaxillary facial angle, an aberrant right subclavian artery, presence of tricuspid regurgitation, reversed a-wave in the ductus venosus, and increased iliac wing angle have not been incorporated into routine screening algorithms and their clinical usefulness in the general population remains uncertain [17]. The role of nuchal translucency measurement in the new era of cell-free fetal DNA screening is also uncertain. It is recommended that a first trimester US for the sole purpose of nuchal translucency screening not be performed in patients with negative cell-free fetal DNA [18]. OR Discussion of Procedures by Variant Variant 1: Routine nuchal translucency measurement at 11 to 14 weeks of gestation for single or twin gestations. Initial imaging. US Duplex Doppler Pregnant Uterus Although the utility of Doppler imaging has been investigated in research protocols, there is no literature to support a recommendation to universally incorporate Doppler studies into routine first trimester screening algorithms for fetal aneuploidy [17].