MEDICINSKI GLASNIK - Aktuelno Ljekarska komora ZE - DO kantona

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Medicinski Glasnik, Volumen 8, Number 1, February 2011
INTRODUCTION
In antenatal protection - monitoring growth and
development of an unborn child, in most European
countries it is recommended to perform three ultrasound
scans: at 9 - 12, 19 - 22 and 29 - 32 weeks
(1). In case of any abnormalities or complications
of pregnancy, additional ultrasound scans could
provide additional safety to pregnant women and
gynecologists monitoring the pregnancy. In search
for specific early ultrasound signs - markers that
could indicate an increased risk of hereditary or
acquired disorders (fetal chromosomopathies), scientific
studies have confirmed an exceptional value
of nuchal fold ultrasound findings (nuchal translucency,
NT) (2). Nuchal fold scan measures fluid
accumulation between the skin and subcutaneous
fascia in the neck of an embryo. It is performed
between 11 and 14 weeks of pregnancy, or when
the crown- rump length (CRL) is 45 to 84 mm (3).
Fold thickness of less than 99 percentile for CRL
is usually tolerated (4). Numerous studies have
shown association between ultrasound findings
of nuchal fold > 3 mm and specific chromosomal
aberrations, especially with aneuploidy and Down
syndrome (5). The correlation of NT scan findings
with Down syndrome is of such importance that
most authors consider nuchal fold scan a screening
procedure for Down syndrome (6). In the study of
King’s group which was done at over 96,000 pregnancies
(22 perinatal centers, 306 gynecologists)
NT scan has indicated Down syndrome in 82%
of fetuses (frequency of false positives: 8.3%)
(7). In addition to association with chromosomal
aberrations, nuchal fold thickness is also used as
a marker for other genetic syndromes, usually heart
anomalies (8). Fetal NT increases with CRL,
therefore, it is very important to take into account
gestation period when determining whether the
measured NT was increased or not (9). In a study
that involved 96,127 pregnancies, the NT median
value and 95-percentile at a crown-rump length of
45 mm were 1.2 and 2.1 mm; the respective values
at a crown-rump length of 84 mm were 1.9 and 2.7
mm (10). In pregnancies with fetal NT below the
99th percentile (3.5 mm), parents’ decision regarding
the determination of the fetal karyotype depended
on the individual risk, accessed based on
maternal age, ultrasound findings and free β-HCG
and PAPP-A in maternal serum between 11-13 +6
weeks (11).
Several prospective interventional studies have
examined implementation of NT screening into
routine clinical practice (12). In our clinic in Kragujevac
since 2008 we have reviewed nuchal fold
thickness of fetuses in all pregnant women as an
integral part of the review at the beginning of the
second trimester of pregnancy. The resulting value
was used to calculate the risk of using combined
test. The aim of this study is to determine the
predictive value of fetal NT measurements in the
detection of chromosomopathy.
PATIENTS AND METHODS
The study was conducted at the Clinic for Gynecology
and Obstetrics of the Clinical Center
in Kragujevac (Serbia) on singleton intrauterine
pregnancies in the first trimester of pregnancy
in the period 2007-2009. A clinical experimental
study model was used. All subjects read and
signed informed consent for participation in this
study. Ethical Committee of the Clinical Center
Kragujevac approved the study.
The investigation included 317 pregnant women
with singleton pregnancies monitored by Genetic
Counselling Service Committee of the Clinic
of Gynaecology and Obstetrics of the Clinical
Center Kragujevac. The study inclusion criteria
involved the crown-rump length (CRL) between
45 and 84 mm and the gestational age of 11-13+6
weeks. For measurements of fetal nuchal translucency
thickness (NT) a high-resolution ultrasound
device Aloka Pro Sound 3500 with a cine-loop
function was used, which allowed replay and
a caliper providing measurements to 1 decimal
point. Only the fetal head and the upper thorax
were scanned. Since the magnification was maximal,
each slight movement of the caliper produced
only a 0.1 mm change. The nuchal translucency
was measured with the fetus in a neutral
position. The maximum thickness of the subcutaneous
translucency between skin and the soft
tissue overlying the cervical spine was measured.
The calipers were placed on the lines defining
the NT thickness so that they can hardly be seen
on a white borderline behind the neck (Figure
1). Several measurements during the scan were
made, but only maximum measurement for the
risk assessment was used. In cases where umbilical
cord was around the fetal neck (in about 8%
of the cases) the NT thickness above and below