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Obstetrics
Diagnosis
Aneuploidy
Trisomy 21
Trisomy 21
Roya Sohaey, MD
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KEY FACTS

  • Imaging

    • Top Differential Diagnoses

      • Clinical Issues

        • Diagnostic Checklist

          TERMINOLOGY

          • Abbreviations

            • Trisomy 21 (T21)

          • Synonyms

            • Down syndrome

          • Definitions

            • Likelihood ratios (LR)
              • Positive LR: ↑ risk of T21 compared with pretest risk due to presence of finding
                • Example: Absent nasal bone (NB) = 23x ↑ risk than a priori risk
              • Negative LR: ↓ risk of T21 compared with pretest risk secondary to absence of finding
                • Example: Normal NB = 50% less risk than a priori risk
            • Sonographic markers for aneuploidy are not anomalies
              • Most occur in normal fetuses

          IMAGING

          • General Features

            • Ultrasonographic Findings

              • Imaging Recommendations

                DIFFERENTIAL DIAGNOSIS

                  PATHOLOGY

                  • General Features

                    CLINICAL ISSUES

                    • Presentation

                      • Demographics

                        • Natural History & Prognosis

                          DIAGNOSTIC CHECKLIST

                          • Consider

                            • Image Interpretation Pearls

                              • Reporting Tips

                                Selected References

                                1. Hu T et al: Prenatal chromosomal microarray analysis in 2466 fetuses with ultrasonographic soft markers: a prospective cohort study. Am J Obstet Gynecol. S0002-9378(20)31269-2, 2020
                                2. Wan JH et al: Use of noninvasive prenatal screening with cell-free DNA in late pregnancy with sonographic soft markers. Eur J Obstet Gynecol Reprod Biol. 252:431-3, 2020
                                3. Winter TC et al: How to integrate cell-free DNA screening with sonographic markers for aneuploidy: an update. AJR Am J Roentgenol. 210(4):906-12, 2018
                                4. Gil MM et al: Analysis of cell-free DNA in maternal blood in screening for aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 50(3):302-14, 2017
                                5. Wiechec M et al: How effective is first-trimester screening for trisomy 21 based on ultrasound only? Fetal Diagn Ther. 39(2):105-12, 2016
                                6. Abele H et al: First trimester ultrasound screening for Down syndrome based on maternal age, fetal nuchal translucency and different combinations of the additional markers nasal bone, tricuspid and ductus venosus flow. Prenat Diagn. 35(12):1182-6, 2015
                                7. Gil MM et al: Analysis of cell-free DNA in maternal blood in screening for fetal aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 45(3):249-66, 2015
                                8. Vos FI et al: Nasal bone length, prenasal thickness, prenasal thickness-to-nasal bone length ratio and prefrontal space ratio in second- and third-trimester fetuses with Down syndrome. Ultrasound Obstet Gynecol. 45(2):211-6, 2015
                                9. Reddy UM et al: Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop. J Ultrasound Med. 33(5):745-57, 2014
                                10. Moreno-Cid M et al: Systematic review of the clinical prediction rules for the calculation of the risk of Down syndrome based on ultrasound findings in the second trimester of pregnancy. Prenat Diagn. 34(3):265-72, 2014
                                11. Agathokleous M et al: Meta-analysis of second-trimester markers for trisomy 21. Ultrasound Obstet Gynecol. 41(3):247-61, 2013
                                Related Anatomy
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                                Related Differential Diagnoses
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                                References
                                Tables

                                Tables

                                KEY FACTS

                                • Imaging

                                  • Top Differential Diagnoses

                                    • Clinical Issues

                                      • Diagnostic Checklist

                                        TERMINOLOGY

                                        • Abbreviations

                                          • Trisomy 21 (T21)

                                        • Synonyms

                                          • Down syndrome

                                        • Definitions

                                          • Likelihood ratios (LR)
                                            • Positive LR: ↑ risk of T21 compared with pretest risk due to presence of finding
                                              • Example: Absent nasal bone (NB) = 23x ↑ risk than a priori risk
                                            • Negative LR: ↓ risk of T21 compared with pretest risk secondary to absence of finding
                                              • Example: Normal NB = 50% less risk than a priori risk
                                          • Sonographic markers for aneuploidy are not anomalies
                                            • Most occur in normal fetuses

                                        IMAGING

                                        • General Features

                                          • Ultrasonographic Findings

                                            • Imaging Recommendations

                                              DIFFERENTIAL DIAGNOSIS

                                                PATHOLOGY

                                                • General Features

                                                  CLINICAL ISSUES

                                                  • Presentation

                                                    • Demographics

                                                      • Natural History & Prognosis

                                                        DIAGNOSTIC CHECKLIST

                                                        • Consider

                                                          • Image Interpretation Pearls

                                                            • Reporting Tips

                                                              Selected References

                                                              1. Hu T et al: Prenatal chromosomal microarray analysis in 2466 fetuses with ultrasonographic soft markers: a prospective cohort study. Am J Obstet Gynecol. S0002-9378(20)31269-2, 2020
                                                              2. Wan JH et al: Use of noninvasive prenatal screening with cell-free DNA in late pregnancy with sonographic soft markers. Eur J Obstet Gynecol Reprod Biol. 252:431-3, 2020
                                                              3. Winter TC et al: How to integrate cell-free DNA screening with sonographic markers for aneuploidy: an update. AJR Am J Roentgenol. 210(4):906-12, 2018
                                                              4. Gil MM et al: Analysis of cell-free DNA in maternal blood in screening for aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 50(3):302-14, 2017
                                                              5. Wiechec M et al: How effective is first-trimester screening for trisomy 21 based on ultrasound only? Fetal Diagn Ther. 39(2):105-12, 2016
                                                              6. Abele H et al: First trimester ultrasound screening for Down syndrome based on maternal age, fetal nuchal translucency and different combinations of the additional markers nasal bone, tricuspid and ductus venosus flow. Prenat Diagn. 35(12):1182-6, 2015
                                                              7. Gil MM et al: Analysis of cell-free DNA in maternal blood in screening for fetal aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 45(3):249-66, 2015
                                                              8. Vos FI et al: Nasal bone length, prenasal thickness, prenasal thickness-to-nasal bone length ratio and prefrontal space ratio in second- and third-trimester fetuses with Down syndrome. Ultrasound Obstet Gynecol. 45(2):211-6, 2015
                                                              9. Reddy UM et al: Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop. J Ultrasound Med. 33(5):745-57, 2014
                                                              10. Moreno-Cid M et al: Systematic review of the clinical prediction rules for the calculation of the risk of Down syndrome based on ultrasound findings in the second trimester of pregnancy. Prenat Diagn. 34(3):265-72, 2014
                                                              11. Agathokleous M et al: Meta-analysis of second-trimester markers for trisomy 21. Ultrasound Obstet Gynecol. 41(3):247-61, 2013