2. Nuchal Translucency Screening
The nuchal (say "NEW-kuhl") translucency screening is a test done during
pregnancy. It uses ultrasound to measure the thickness of the fluid buildup
at the back of the developing baby's neck. If this area is thicker than normal,
it can be an early sign of Down syndrome, trisomy 18, or heart problems.
The test is done between 10 and 13 weeks of pregnancy. It may be done as
part of the first trimester screening test or the integrated screening test.
This test shows the chance that a baby may have a certain problem. It can't
show for sure that a baby has a problem. You would need a diagnostic test,
such as chorionic villus sampling (CVS) or amniocentesis, to find out for
sure if the baby actually has a problem.
3.
4. The NT scan is an ultrasound done in the first trimester to determine your
baby's risk of having Down syndrome and some other chromosomal
abnormalities. It's usually done along with a blood test. If the nuchal
translucency test indicates that your baby may have a health condition, you can
decide whether to have a diagnostic test to find out for certain.
doctor is doing an ultrasound scan on pregnant woman
Photo credit: Thinkstock
IN THIS ARTICLE
• What is the nuchal translucency test?
• How is the nuchal translucency test done?
• How are NT scan results calculated?
• What do NT scan results mean?
• How accurate is the nuchal translucency test?
• What happens if my NT scan indicates a problem?
• What is the nuchal translucency test?
5. The nuchal translucency test (also called the NT scan) uses ultrasound to assess your developing baby's risk of having
Down syndrome (DS) and some other chromosomal abnormalities, as well as major congenital heart problems. It's offered
to all pregnant women, along with a blood test, in first-trimester combined screening options.
The NT scan measures the clear (translucent) space in the tissue at the back of your baby's neck. (This is the "nuchal
translucency.") Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester,
causing this clear space to be larger than average.
6.
7. cfDNA (Cell-Free DNA)
Cell-free DNA screening is a test that can determine if a woman
has a higher chance of having a fetus with Down syndrome
(trisomy 21), trisomy 18, trisomy 13 or an abnormality in the sex
chromosomes (X and Y chromosomes). With this test, a sample
of the woman's blood is taken after 10 weeks of pregnancy.
FAQ: Cell-Free DNA Screening | Patient Education | UCSF
Health
8. What causes cfDNA?
The release of cfDNA into the bloodstream appears by different
reasons, including the primary tumor, tumor cells that circulate in
peripheral blood, metastatic deposits present at distant sites, and
normal cell types, like hematopoietic and stromal cells
9. cfDNA (Cell-Free DNA)
Nuchal translucency screening
Timing: 11-14 weeks
Process: ultrasound to assess thickness as fetus’s neck, maternal blood draw
Risk: noninvasive, ultrasound and maternal blood draw
Results: screening test for down syndrome, trisomy 18 & 13
cfDNA
Timing: 11+ weeks, can be done as early as 7 weeks
Process: maternal blood draw, fetal cell fragments in maternal blood are assessed
Risk: noninvasive, ultrasound and maternal blood draw
Results: screening test for abnormal amounts of chromosomes and microdeletions
in fetal DNA
10. Karyotyping Test
Karyotyping is a test to examine chromosomes in a sample of cells. This
test can help identify genetic problems as the cause of a disorder or
disease.
How the Test is Performed
The test can be performed on almost any tissue, including:
Amniotic fluid
Blood
Bone marrow
Tissue from the organ that develops during pregnancy to feed a growing baby
(placenta)
To test amniotic fluid, an amniocentesis is done.
A bone marrow biopsy is needed to take a sample of bone marrow.
11. The sample is placed into a special dish or tube and allowed to grow in the
laboratory. Cells are later taken from the new sample and stained. The
laboratory specialist uses a microscope to examine the size, shape, and
number of chromosomes in the cell sample. The stained sample is
photographed to show the arrangement of the chromosomes. This is called
a karyotype.
Certain problems can be identified through the number or arrangement of
the chromosomes. Chromosomes contain thousands of genes that are
stored in DNA, the basic genetic material.
