DR/ AKRAM ABD ELGHANY MD , ALAZHAR UNIVERSITY CONSULTANT OBS.

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DR/ AKRAM ABD ELGHANYMD , ALAZHAR UNIVERSITY
CONSULTANT OBS.GYN. PORTSAID
G.HOSPITAL
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Nuchal TRANSLUCENCY
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Nuchal Translucency
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• Nuchal translucency (NT)
• This is a collection of fluid under the skin
  behind the neck of fetuses at 11-136 weeks that
  can be measured by ultrasound examination.

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• The term translucency is used, irrespective
  of whether it is
• septated or not,
• confined to the neck, or
• envelopes the whole fetus.
• NT is increased in fetuses with chromosomal
  abnormalities, cardiac defects, certain genetic
  syndromes.

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During the second trimester the translucency
usually resolves or it evolves into nuchal
edema or cystic hygromas with or without
generalized hydrops.
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Increased fetal NT thickness at 11136 weeks is
a common phenotypic expression of chromosomal
defects and a wide range of fetal malformations
and genetic syndromes.
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The incidence of chromosomal and other
abnormalities is related to the size, rather than
the appearance of NT.
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the correlation between nuchal translucency and
fetal anomalies and perinatal risk is One of the
single most important breakthroughs in birth
defect screening
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Pathophysiology of increased NT Cardiac
dysfunction Venous congestion in the head and
neck Altered composition of the extracellular
matrix Failure of lymphatic drainage Fetal
anemia Fetal hypoproteinemia Fetal infection.
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PATHOPHYSIOLOGY OF INCREASED FETAL NT

• The heterogeneity of conditions associated with
  increased NT
• suggests that there may not be a single
  underlying mechanism for
• the collection of fluid under the skin of the
  fetal neck.

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measurement
Image
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• The optimal gestational age for measurement of
  fetal NT is 11 weeks to 13 weeks and 6 days.
• The minimum fetal crownrump length should be 45
  mm and the maximum 84 mm.

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• Transabdominal ultrasound is successed in 95 of
  cases.
• Transvaginal sonography in the others.
• The results from transabdominal and transvaginal
  scanning are similar.

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• A mid-sagittal section of the fetus.
• the fetus is in the neutral position.

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• Only the fetal head and upper thorax should be
  included in the image.
• The magnification should be as large as possible.

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• Care must be taken to distinguish
• between fetal skin and amnion.
• This is achieved by
• spontaneous fetal movement.
• asking the mother to cough
• tapping the maternal abdomen.

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The maximum thickness of the subcutaneous
translucency between the skin and the soft tissue
overlying the cervical spine should be measured.
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• The callipers should be placed on the lines that
  define the NT thickness .
• the crossbar of the calliper merges with the
  white line of the border and not in the nuchal
  fluid.

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• more than one measurement must be taken.
• the maximum one should be recorded.
• It is good practice to retain at least one image
  for your patient records.

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• In normal fetuses NT thickness increases with
  fetal crown-rump length (CRL).
• Increased NT refers to a measurement above the
  95th centile.

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• The median and 95th centile of NT at a CRL of 45
  mm are 1.2 and 2.1 mm.
• the respective values at CRL of 84 mm are 1.9 and
  2.7 mm.
• The 99th centile does not change with CRL and it
  is 3.5 mm.
• (Snijders et al 1998).

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• NT should be measured with the fetus in the
  neutral position.
• When the fetal neck is hyperextended the
  measurement can be increased by 0.6 mm.
• when the neck is flexed, the measurement can be
  decreased by 0.4 mm.

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• Screening for chromosomal defects in the first,
  rather than the second trimester, has the
  advantage of
• earlier prenatal diagnosis.
• less traumatic termination of pregnancy.

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Disadvantage of earlier screening Identifies
chromosomally abnormal pregnancies that are
destined to miscarry.
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NUCHAL FOLD

• The skin thickness in the posterior aspect of the
  fetal neck .
• should be distinguished from cystic hygroma, in
  which the skin in this area has fluid-filled
  loculations.
• should not be confused with nuchal translucency.

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• Nuchal fold measurement
• transverse section of the fetal head at the
  level of the cavum septum pellucidum and thalami,
  angled posteriorly to include the cerebellum.
• from the outer edge of the occiput bone to the
  outer skin limit in the midline.

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• Thickened nuchal fold
• 6 mm between 18 and 24 weeks
• 5 mm at 16 to 18 weeks.
• Evaluation of the nuchal fold should be
  considered during the screening ultrasound at 16
  to 22 weeks gestation.

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• Evaluation of the nuchal fold should be
  considered during the screening ultrasound at 16
  to 22 weeks gestation.
• A nuchal fold of 6mm or greater at 18 to 24 weeks
  or of 5mm or greater at 16 to 18 weeks should be
  considered significant and should prompt referral
  for validation and consultation.

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• The finding of an isolated thickened nuchal fold
  increases the risk for
• fetal aneuploidy.
• fetal karyotyping should be offered.

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• The prevalence of
• chromosomal defects,
• miscarriage
• fetal death
• major fetal abnormalities.
• Increased exponentially with NT thickness.

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the King's College researchers in London, Their
data, now extending to well over 400,000 cases,
shows 82 nuchal translucency Down syndrome
detection, with comparable percentages for
trisomies 13 and 18.
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• chromosomal defects
• increases with NT thickness
• 50 trisomy 21.
• 25 trisomy 18 or 13.
• 10 Turner syndrome.
• 5 triploidy .
• 10 other chromosomal defects (Snijders et al
  1998).

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fetal NT screening identified more than 75 of
fetuses with trisomy 21 and other major
chromosomal defects for a false positive rate of
5. the detection rate was about 60 for a false
positive rate of 1 (Nicolaides 2004).
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normal karyotype
fetal death increases with
NT thickness

• 1.3 with NT between the 95th and 99th
  centiles.
• 20 for NT of 6.5 mm or more.
• The majority of fetuses that die do so by 20
  weeks and they usually show progression to
  hydrops.

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• major fetal abnormalities
• 1.6, in those with NT below the 95th centile,
• 2.5 for NT between the 95th
• and 99th centiles ,
• 45 for NT of 6.5 mm or more (Souka et al
  2001).

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the prevalence of major cardiac Abnormalities,
diaphragmatic hernia, exomphalos, body stalk
anomaly, skeletal abnormalities, and certain
genetic syndromes,such as congenital adrenal
hyperplasia, Noonan syndrome, appears to be
higher than in the general population.
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Developmental Delay Studies on the long term
follow up of chromosomally and anatomically
normal fetuses with increased NT reported that
The prevalence of developmental delay is 24
(Souka et al 2004).
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MAJOR CARDIAC DEFECT

• In chromosomally normal fetuses, the prevalence
  of major cardiac
• defects increases exponentially with NT
  thickness

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• 1.6 per 1,000 for NT below the 95th
  centile.
• 1 forNT of 2.53.4 mm.
• 3 for NT of 3.54.4 mm.
• 7 for NT of 4.55.4 mm.
• 20 for NT of 5.56.4 mm.
• 30 for NT of 6.5 mm or more (Souka et al
  2004).

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increased NT constitutes an indication for
specialist fetal echocardiography. the overall
prevalence of major cardiac defects in such a
group of fetuses (12) is similar to that found
in pregnancies affected by maternal diabetes
mellitus or with a history of a previously
affected off spring, which are well accepted
indications for fetal echocardiography.
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• Increased NT 99th centile constitutes an
  indication for specialist fetal echocardiography
  .
• In this population the prevalence of major
  cardiac defects would be very high.

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The best strategy of screening for major cardiac
abnormalities is to carry out specialist fetal
echocardiography in patients with increased NT at
11136 weeks and in those with an
abnormal four-chamber view in the routine
mid-trimester scan.
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Body stalk anomaly

• NT is increased in about 85 of the cases,
• the karyotype is usually normal.

• found in about 1 in 10,000 at
• 10136 weeks.
• The ultrasonographic features are
• major abdominal wall defect,
• severe kyphoscoliosis,
• short umbilical cord with a single artery.

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Diaphragmatic hernia

• Increased NT in
• 40 of fetuses.
• 80 of neonatal death due to pulmonary
  hypoplasia .
• 20 of the survivors.
• (Sebire et al 1997).

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Exomphalos

• NT Increased in
• 85 of chromosomally abnormal,
• 40 of chromosomally normal fetuses.
• At 11136 weeks the incidence of exomphalos is 1
  in 1,000 .
• the incidence of chromosomal defects, mainly
  trisomy18, is about 60 (Snijders et al 1995).

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Megacystis

• NT increased in
• 75 in chromosomal abnormalities mainly trisomy
  13.
• 30 normal karyotype .
• (Liao et al 2003).

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MANAGEMENT OF PREGNANCIES WITH INCREASED NT
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The vast majority of fetal abnormalities
associated with increased NT can be diagnosed by
a series of investigations that can be completed
by 14 weeks of gestation.

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• The parents can be reassured that the chances of
  delivering a baby with no major abnormalities is
• 90 for NT between the 95th- 99th.
• 70 for NT of 3.54.4 mm.
• 50 for NT of 4.55.4 mm.
• 30 for NT of 5.56.4 mm.
• 15 for NT of 6.5 mm or more.

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• It is possible to estimate, for each NT group,
  the chances of intrauterine survival and delivery
  
• of a healthy baby with no major defects.

• These data are useful in counselling parents of
  pregnancies with increased NT and in the follow
  up investigations.

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