Nuchal Translucency

1. See Also
   1. Antenatal Screening
   2. Trisomy Findings on Fetal Ultrasound
2. Definitions
   1. Nuchal Translucency
      1. Posterior fetal neck lucency by Ultrasound
3. Indications
   1. Early Antenatal Screening for Down Syndrome and birth defects
4. Protocol
   1. Timing: 11-13 weeks gestation
   2. Technique
      1. Ultrasound used to measure the lucency of the posterior fetal neck
      2. Measurement requires additional special training and certification
5. Precautions
   1. Do not use Nuchal Translucency alone (combine with serum Aneuploidy Screening)
      1. Exception: Multiple Gestation pregnancies (serum testing is inaccurate)
   2. Abnormal Nuchal Translucency is associated with both Aneuploidy and structural defects
      1. Obtain detailed Fetal SurveyUltrasound at 18 to 22 weeks if abnormal Nuchal Translucency
      2. Obtain fetal Echocardiogram if abnormal Nuchal Translucency (per ACOG guidelines)
6. Efficacy: Down Syndrome detection
   1. Test Sensitivity: 70%
   2. Test Specificity: >95%
7. Differential Diagnosis: Increased Nuchal Translucency
   1. Down Syndrome and other Genetic Syndromes
   2. Major Congenital Heart Defect
   3. Great Vessel defect
   4. Fetal malformations, dysplasias, deformations and disruptions
   5. False Positives (Nuchal Translucency increases 15-20% per week in normal pregnancies)
8. References
   1. Anderson (2009) Am Fam Physician 79(2): 117-24 [PubMed]
   2. Makrydimas (2005) Am J Obstet Gynecol 192(1): 89-95 [PubMed]
   3. Salvedt (2005) Ultrasound Obstet Gynecol 25(6): 537-45 [PubMed]
   4. Souka (2005) Am J Obstet Gynecol 192(4):1005-21 [PubMed]