Point 1:-What is meant by NT? Ans:- 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 a) septated or not and b) whether it is confined to the neck or envelopes
the whole fetus. 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. In fetuses with chromosomal
abnormalities, cardiac defects and many genetic syndromes the NT thickness is
increased.
Point 1:- What is the Detection rate:??---Screening
by NT can detect about 80% of fetuses with trisomy 21 and other major
aneuploides for a false positive rate of 5%.
The
combination of NT and maternal serum free β-hCG and PAPP-A improves the
detection to 90%. But if the nasal bone, ductus venosus flow and
tricuspid flow. Are included then the
detection rate can increase to about 95% and the false positive
rate can be reduced to 3%
Early screening for chromosomal abnormalities
:
Q. 2:-Where to send serum of pregnant
mother for double marker?? Ans:-Measurement of maternal serum free β-hCG and
PAPP-A by laboratories that can demonstrate good quality assurance performance.
A risk calculation
program that uses an algorithm based on scientific evidence. The software
companies that use this algorithm are Astraia Software GmbH, ViewPoint GE Healthcare and Zeitgeist Health SE.
1.
Appropriate counseling
of the parents.
Software is
important for risk calculation:
Software is for first-trimester screening for chromosomal
abnormalities by a) maternal age, b) fetal NT thickness and c) maternal serum
free β-hCG and d) PAPP-A. Should they wish to use the additional markers for
chromosomal abnormalities (nasal bone, tricuspid flow and ductus venosus flow) they
may do so.
Normal nuchal
translucency
Head up
High nuchal
translucency
Head up on
1.
.
Protocol for measurement
- The gestational period must be
11 to 13 weeks and six days.
- The
fetal crown-rump length should be between 45 and 84mm.
- The
magnification of the image should be such that the fetal head and thorax
occupy the whole screen.
- 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
maxilla.
- 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.
- Care
must be taken to distinguish between fetal skin and amnion.
- The
widest part of translucency must always be measured.
- 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.
- 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.
- 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.
- The umbilical
cord may be round the fetal neck 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
- the FMF software for the calculation of risks. In addition to the FMF audit, all
sonographers are encouraged to perform their own internal quality
assurance on a monthly basis by examining their NT distribution using the
automated audit module incorporated within the FMF risk calculation
software.
- The
name of the sonographer will be removed from the FMF website list of
holders of the Certificate of competence in NT. their FMF software license
will be revoked. In such case the sonographer will need to be retrained
and apply for recertification by attending the FMF internet based course
on the 11-13 weeks scan and submitting the appropriate logbook of images.
·
he first trimester screening is a safe,
optional test for all pregnant women. It's a way of checking
your baby's risk of certain birth defects, such as Down syndrome, Edward's
syndrome (trisomy 18), trisomy 13 and many other chromosomal
abnormalities as well as heart problems.
·
What the Test Does
·
The screening
involves two steps. A blood test checks for levels of two
substances -- pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin. A special ultrasound, called a nuchal translucency
screening, measures your baby's nasal bone as well as the fluid at the back of
your baby's neck. A high volume of fluid can be a sign of problems.
·
The combined
result of the blood tests and the ultrasound gives you
a sense of your baby's risk. However, it's not a diagnosis. Most women who have
an abnormal firsttrimester screening go on to have healthy babies.
·
Whether you get
this test is your choice. Some women want the test so they can prepare. Others
don't. They may decide that knowing the results wouldn't change anything. Or
they feel that the test could result in unnecessary stress and invasive
testing. However knowing of possible risks would allow for increased monitoring
during your pregnancy as well as giving you delivery options (special hospital,
pediatric surgeon availability).
·
How the Test Is Done
·
The first
trimester screen won't harm you or your baby. A technician will take a quick
blood sample from your arm or fingertip. The nuchal translucency screening is a
normal ultrasound. You'll lie on your back while a technician holds a probe
against your belly. It will take between 20 to 40 minutes.
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