Pregnancy Level I scan / NT-NB Scan

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Pregnancy Level I scan / NT-NB Scan
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• What is a nuchal translucency / Level I scan?
• It is a screening test in form of ultrasound scan
  done from 11 to 14 weeks of pregnancy. To be
  precise it is done from 11 weeks 3 days to 13
  weeks 6 days of pregnancy. It is usually done
  along with a blood test called dual marker and
  these both form a combined screening test.
• It is known as NT /NB scan as doctor measures the
  nuchal anslucency (NT) and nasal bone (NB) of the
  fetus. It is also commonly known by name of
  level-I scan. The radiologist measures a
  fluid-filled space behind your babys neck known
  as nuchal transluceny. This measurement can help
  to detect the risk of your baby having a
  chromosomal abnormality such as Down syndrome.
• In addition to nuchal translucency the doctor
  looks for nasal bone of fetus. Absent or short
  nasal bone indicates the possibility of
  underlying chromosomal abnormalities
• Other things like developing limbs, stomach
  bubble, intracranial structures, developing spine
  , placenta, cervical length etc are also assessed
  in the same scan. Some structural abnormalities
  can be ruled out in this scan like absent limbs,
  skeletal abnormalities , any abdominal wall
  defect with protrusion of the abdominal contents
  out etc. So its a type of early scan to rule out
  some abnormalities which are lethal and there is
  no point in carrying the pregnancy further.

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• In addition to these now a days pre-eclamsia
  screening is routinely done with the NT/NB scan.
  It helps to assess the risk of patient of
  developing hypertension ( increased blood
  pressure) in the course of pregnancy. In case of
  high risk the obstetrician gives some
  prophylactic drugs to the patient.
• Pre-eclampsia is a very common cause of bad
  obstetrics outcone like intrauterine fetal
  demise, growth restriction, premature deliveries
  etc.
• In case this is your first scan it gives the
  additional information about the site of
  pregnancy and the exact dating.
• So all in all its a very useful non invasive
  test and every patient must be recommended this
  scan to rule out underlying problems fetus may
  have.It also gives reassurance to the mother that
  everything inside is going fine and relieve her
  of undue stress.
• What are the indications and right time to get NT
  /NB scan?
• Now a days with the advancement of the medical
  field it is a routine to get level I USG for all
  the expecting mothers whether there is any
  history of any congenital abnormality in previous
  issues or not.

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• The importance increases if the maternal age is
  high, previous history of birth defects ,
  previous fetal demise, maternal high BP and
  diabetes.
• A nuchal translucency scan is done between 11 and
  14 weeks of pregnancy. Ideally the time is
  11weeks 3 days to 13 weeks 6 days.
• What to expect and how to prepare yourself while
  going for nuchal translucency scan.
• The first thing is you need not be fasting before
  going for scan. Many patients starve themselves
  before these scan and end up feeling miserable.
  There is no role of fasting in the obstetric
  scan.
• You need to drink some water and you must have
  moderately full urinary bladder. There is no need
  to have extra-full bladder, just moderate
  pressure will be good for the scan.
• Normally the scan is done trans- abdominally. The
  radiologist will apply some gel and gently move
  the ultrasound probe across your abdomen. Usually
  it takes about 15-20 minutes for the scan.
  However it all depends on the position of your
  baby. If the position is favorable the scan can
  be done easily in one go. Many a times you will
  have to wait until the baby lies in the favorable
  position required by the radiologist. You may be
  asked to come repeatedly in the ultrasound room
  after waiting for some time.

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• Some times trans vaginal ultrasound needs to be
  done for better visualization of the fetus. In
  that case ultrasound probe is gently inserted
  into your vagina which may feel a bit
  uncomfortable but usually is not painful.
• What does the results tell?
• The NT/NB scan results are usually combined with
  a blood test ( Dual markers) and these both
  assess the combined risk of chromosomal disorders
  in pregnancy.
• Remember that a normal screening result (screen
  negative) isnt a guarantee that your baby has
  normal chromosomes, but it does suggest that a
  problem is unlikely. Likewise, an abnormal
  screening result (screen positive) doesnt mean
  that your baby has a chromosomal problem just
  that your baby is more likely to have one. Most
  screen-positive babies turn out not to have a
  problem Only about a third of babies with an
  increased nuchal translucency measurement turn
  out to have chromosomal defects.
• Results are usually reported as low risk or
  high risk. If the result comes out to be low
  risk then the pregnancy is considered to be
  normal and no further tests are usually done.

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If the result comes to be moderate or high risk
then further assessment is done by invasive
procedures such as chorionic venous sampling and
amniocentesis which will give you a definitive
result. A non invasive blood test know as NIPT
(Non invasive prenatal testing) is also available
now a days to diagnose the chromosomal
abnormalities. Your obstetrician or genetic
counselor will help you to choose between these
tests. Article Resource - https//www.apexdiagno
stics.in/blog/pregnancy-level-i-scan-nt-nb-scan/