1. Nuchal Translucency (NT) Screen Ernest F. Talarico, Jr., Ph.D. Associate Director of Medical Education Associate Professor of Anatomy & Cell Biology Associate Faculty, Radiologic Sciences Indiana University School of Medicine-Northwest Campus Dunes Medical Professional Building Gary, Indiana 46408-1197 Fall 2013

2. Nuchal translucency (NT) is the sonographic appearance of a collection of fluid under the skin behind the fetal neck in the first-trimester of pregnancy. The term translucency is used, irrespective of whether it is septated or not and whether it is confined to the neck or envelopes the whole fetus. In fetuses with chromosomal abnormalities, cardiac defects and many genetic syndromes, the NT thickness is increased.

3. the calculation of risk of chromosomal abnormalities by a combination of – maternal age, – fetal NT, – first-trimester maternal serum free β-hCG: human chorionic gonadotropin (hCG) – is a hormone produced during pregnancy that is made by the developing placenta after conception, and later by the placental component syncytiotrophoblast. Pregnancy-associated plasma protein A, pappalysin 1 (PAPP- A): – secreted metalloproteinase which cleaves insulin-like growth factor binding proteins (IGFBPs).

4. 12 Point Protocol for Measurement of Nuchal Translucency 1.The gestational period must be 11 to 13 weeks and six days. 2.The fetal crown-rump length should be between 45 and 84mm. 3.The magnification of the image should be such that the fetal head and thorax occupy the whole screen. 4.A mid-sagittal view of the face should be obtained. This is defined by the presence of the echogenic tip of the nose and rectangular shape of the palate anteriorly, the translucent diencephalon in the centre and the nuchal membrane posteriorly. Minor deviations from the exact midline plane would cause non-visualization of the tip of the nose and visibility of the zygomatic process of the maxilla. 5.The fetus should be in a neutral position, with the head in line with the spine. When the fetal neck is hyperextended the measurement can be falsely increased and when the neck is flexed, the measurement can be falsely decreased. 6.Care must be taken to distinguish between fetal skin and amnion.

5. 12 Point Protocol for Measurement of Nuchal Translucency 7.Measurements should be taken with the inner border of the horizontal line of the callipers placed ON the line that defines the nuchal translucency thickness - the crossbar of the calliper should be such that it is hardly visible as it merges with the white line of the border, not in the nuchal fluid. 8.In magnifying the image (pre or post freeze zoom) it is important to turn the gain down. This avoids the mistake of placing the calliper on the fuzzy edge of the line which causes an underestimate of the nuchal measurement. 9.During the scan more than one measurement must be taken and the maximum one that meets all the above criteria should be recorded in the database. 10.A new approach for the measurement of NT which improves the accuracy of measurements, is with the use of a semi-automated technique. The operator places a box in the nuchal area and the machine automatically selects the best measurement, which uses an algorithm that draws a line through the center of the nuchal membrane and another line at the edge of the soft tissue overlying the cervical spine. The measurement obtained by this method is similar to that obtained manually and it is therefore applicable to the software of the Fetal Medicine Foundation. 11.The umbilical cord may be round the fetal neck (nuchal cord) in about 5% of cases and this finding may produce a falsely increased NT. In such cases, the measurements of NT above and below the cord are different and, in the calculation of risk, it is more appropriate to use the average of the two measurements

6. Measurement of the Nuchal Translucency There are several steps that hat the physician should consider when performing the ultrasound examination during the first trimester. They are as follows: 1.The magnification of the image should be as large as possible and the calipers able to produce 0.1 mm changes in the measurement. 2.The nuchal translucency measurement should be obtained between 11 weeks and 13 weeks six days which would be equivalent to a crown-rump length between 45 and 84 millimeters Crown-Rump Length Measurement

7. Measurement of the Nuchal Translucency 3.A sagittal section of the fetus should be obtained, in a neutral position. 4.The widest part of the translucency should be measured. The widest nuchal translucency measurement should be made, as indicated in this example by the green arrows.

8. Measurement of the Nuchal Translucency 5.Measurements should be taken with the horizontal lines placed on the lines that define the nuchal translucency thickness This image compares the actual specimen with the ultrasound measurement of the nuchal translucency.

9. Measurement of the Nuchal Translucency Example of an Abnormal Nuchal Translucency Measurement The fetus on the left has a normal nuchal translucency measurement (green line). The fetus on the right has an increased nuchal translucency measurement (green line) 2.5 mm and 3.0 mm

10. This illustrates the anatomy of a first-trimester fetus using optical lighting, an MRI scan, and ultrasound. The nuchal translucency is located posterior to the back of the skull and neck. It is translucent, and contains fluid. This represents three imaging modalities that identify early fetal development. The fetus on the left is an actual fetus at 12 weeks. The fetus in the middle is from an MRI study and the fetus on the right is an ultrasound. The blue areas behind the neck represent the nuchal translucency that is measured during the first-trimester scan when evaluating the fetus for Down syndrome and other birth defects.

13. Nuchal Cord A nuchal cord occurs when the umbilical cord becomes wrapped around the fetal neck 360 degrees. Nuchal cords are very common, with prevalence rates of 6% to 37%. Up to half of nuchal cords resolve before delivery. Classification: 1.A "Type A" nuchal cord is wrapped around the neck 360 degrees. 2.A "Type B" pattern is described as a hitch which cannot be undone and ends up as a true knot.

14. Nuchal Cord Note the different thickness of the nuchal translucency above and below the nuchal cord. The umbilical cord may be round the fetal neck in 5– 10% of cases and this finding may produce a falsely increased nuchal translucency (may add 0.8mm to the measurement). In such cases, the measurements of nuchal translucency above and below the cord are different and, in the calculation of risk, it is more appropriate to use the smaller measurement.

16. Clinical Correlations Increased nuchal translucency – Normal Karyotype.

17. Increased nuchal translucency – Down Syndrome

18. Increased nuchal translucency – Trisomy 18

19. Trisomy 18 – Edwards Syndrome Causes, incidence, and risk factors – Trisomy 18 is a somewhat common syndrome. It is three times more common in girls than boys. Symptoms – Clenched hands – Crossed legs – Feet with a rounded bottom (rocker- bottom feet) – Low birth weight – Low-set ears – Mental delay – Poorly developed fingernails – Small head (microcephaly) – Small jaw (micrognathia) – Undescended testicle – Unusual shaped chest (pectus carinatum)

20. Questions?