II. Definitions
- Nuchal Translucency
- Posterior fetal neck lucency by Ultrasound
III. Indications
- Early Antenatal Screening for Down Syndrome and birth defects
IV. Protocol
- Timing: 11-13 weeks gestation
- Technique
- Ultrasound used to measure the lucency of the posterior fetal neck
- Measurement requires additional special training and certification
V. Precautions
- Do not use Nuchal Translucency alone (combine with serum Aneuploidy Screening)
- Exception: Multiple Gestation pregnancies (serum testing is inaccurate)
- Abnormal Nuchal Translucency is associated with both Aneuploidy and structural defects
- Obtain detailed Fetal SurveyUltrasound at 18 to 22 weeks if abnormal Nuchal Translucency
- Obtain fetal Echocardiogram if abnormal Nuchal Translucency (per ACOG guidelines)
VI. Efficacy: Down Syndrome detection
- Test Sensitivity: 70%
- Test Specificity: >95%
VII. Differential Diagnosis: Increased Nuchal Translucency
- Down Syndrome and other Genetic Syndromes
- Major Congenital Heart Defect
- Great Vessel defect
- Fetal malformations, dysplasias, deformations and disruptions
- False Positives (Nuchal Translucency increases 15-20% per week in normal pregnancies)