Increased NT is associated with a spectrum of fetal abnormalities.
The commonest association is with chromosomal defects. In fetuses
with increased NT and a normal karyotype, the risk of an adverse
outcome remains and increases with increasing NT.
Best practice Key guidelines
(by Shanthi Sairam a,âŽ, Julene S. Carvalho a,b,c,
** a Fetal Medicine Unit, St. George’s Hospital NHS Trust, Blackshaw Road, London SW17 0QT, United Kingdom
** b St. George’s University of London, United Kingdom
** c Royal Brompton Hospital NHS Foundation Trust, United Kingdom
Early fetal echocardiography and anomaly scan in fetuses with increased nuchal translucency
Early Human Development 88 (2012) 269â€“272)
- â€¢ There is clear evidence that pregnancies with increased fetal NT
thickness and normal karyotype are at higher risk of adverse outcome, cardiac or otherwise.
- â€¢ Abnormalities affecting the cardiovascular system are the most
common defects encountered in chromosomally normal fetuses
with increased NT.
- â€¢ Importantly, when abnormalities of all other systems (extra-cardiac)
are put together, the overall number of defects is higher than cardiac
- â€¢ Early fetal echocardiography and early anomaly scan should be
considered in these fetuses.
- â€¢ Each fetal medicine unit should aim to design a management protocol which
is evidence-based but also takes into account expertise and facilities available locally.
- â€¢ A simple protocol, with clear instructions to non-medical as well as
medical staff regarding arrangements for follow up scans for pregnancies
with increased NT and normal karyotype should be in place.
- â€¢ Patients need to be informed of the plan of follow up in their pregnancy
for the increased NT and the need for several scans to rule out
associated structural defects in the baby.
- â€¢ Patients also need to be informed, that in the presence of increased
NT and a normal anomaly scan and fetal echo by 21â€“23 weeks,
there is a 95% chance of a good outcome.
- â€¢ Patients need to be aware that in a small percentage of pregnancies
(about 5%), some genetic or syndromic causes may be identiï¬ed
postnatally, even with normal ï¬ndings in the antenatal scans.
6. Research directions
- â€¢ The role of three-dimensional and four-dimensional scan (STIC,
spatio-temporal image correlation) in the presence of increased
NT needs to be explored. Once a volume is acquired, this can be
remotely accessed and analyzed and may address the problem of
lack of expertise particularly with a view to making more technicians
available to screen the fetal hearts at an early gestation.
- â€¢ All units need to audit their practices regularly in order to ensure
that they are up to date with current recommendations and evidence and
to ensure that they deliver the intended services.
- â€¢ Focus needs to shift from using the 11 to 14 week scan as a screening
platform for just Down syndrome to using it as a screening platform for
most structural defects.
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