Transcript In the name of god First Trimester Screening Dr.M.Moradi

In the name of god
First Trimester Screening
Dr.M.Moradi
First Trimester Screening
A method to identify women at risk for having
an aneuploid fetus from the general
population
 Also can identify other birth defects such as
congenital heart defects and diaphragmatic
hernia
 Performed during 11-14 weeks gestation
 Patient Preferences and earlier diagnosis/
reassurance

All patients have a 2% to 3% risk of birth
defects, regardless of their prior history,
family history, maternal age, or lifestyle.
 Chromosome abnormalities account for
approximately 10% of birth defects.
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A detailed fetal anatomic survey
performed at 18 to 22 weeks remains the
primary means for detecting the majority
of serious ‘‘structural’’ birth defects.
 first-trimester screening at 11 to 14
weeks has developed into the initial
screening test for many patients.
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The primary advantage of first trimester
screening is earlier diagnosis of
abnormalities (or early reassurance of the
anxious patient), with the option of an
earlier and safer pregnancy termination.
Advantages of 1st Trimester Screening
Information earlier, more options
 Reduce number of invasive procedures
 May identify other severe anomalies (or risk
for) at time of scan and increased risk of
adverse pregnancy outcome—referral for
2nd Δ evals.
 Good time to date pregnancy accurately
 NT good for multiple gestation
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First Trimester Screening
GOALS of this screen:
 To increase sensitivity,
decrease false-positive rates
 To decrease number of
“unnecessary” invasive
prenatal diagnosis tests.
 NOT to increase number of
elective abortions.
 U/S measurements (NT) and
free B-hCG, PAPP-A
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Use of the guidelines proposed by the
Fetal Medicine Foundation have resulted
in a high consistency in results
Nuchal translusency
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History
◦ Dr.langdon Down 1866
◦ 1980s
◦ 1992…..prof Nicolaid….
Normal range?
 Mechanism?
 Normal Karyotype with increased NT
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The mechanism for increased NT may
vary with the underlying condition. The
most likely causes include heart strain or
failure and abnormalities of lymphatic
drainage . Evidence for heart strain
includes the finding of increased levels of
atrial and brain natriuretic peptide mRNA
in fetal hearts among trisomic fetuses
Nuchal Translucency
Measurements must be
performed by certified
individual!
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True sagital
Position
Caliper
Separation of amnion
magnification
The normal range for NT
measurements is gestational age
dependent.
the median NT increases from 1.3
mm at a crown-rump length (CRL) of
38 mm to 1.9 mm at a CRL of 84 mm.
The 95th percentile increases from 2.2
mm at a crown rump length of 38 mm
to 2.8 mm at a CRL of 84 mm.
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The ability to measure NT and obtain
reproduciblen results improves with
training; good results are achieved after
80 and 100 scans for the transabdominal
and the transvaginal routes, respectively
screening
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Basic
◦ NT
◦ BIOCHEMISTRY
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Advanced
The two most effective maternal serum markers
currently used in the first trimester are pregnancyassociated plasma protein A (PAPPA)
and free B-human chorionic gonadotrophin
(B-hCG).
Maternal serum free b-human chorionic
gonadotropin (b-hCG) normally decreases with
gestation after 10 weeks and maternal serum
PAPP-A levels normally increase.
Levels of these two proteins tend to be increased and
decreased, respectively, in pregnancies affected by
trisomy 21.
PAPP-A and Free BhCG
On average, baby with trisomy 21 will have 2.0 Mom for B-hCG and 0.4 MoM
PAPP-A
Basic screening
High risk 1/50
 Moderate risk
 Low risk 1/1ooo
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Advanced
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Nasal bone
Facial angle
Ductus venosus
Tricuspid regurgitation
Professor
Kypros
Nicolaides.
The fetal nasal bone can be
visualized by sonography at
11–13+6 weeks of gestation
(Cicero et al 2001). Several
studies have demonstrated a
high association between
absent nasal bone at 11–13+6
weeks and trisomy 21, as well
as other chromosomal
abnormalities.
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Three line
Fronto maxillary angle
GA dependent
 CRL=45mm, 84’
 CRL=84mm, 76’
 Above 95% for age=increased risk of
trisomy
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Ductus venosus
Sample size
 Angle
 Filter
 sweep speed
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Tricuspid regurgitation
Fetal heart rate
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In normal pregnancy, the fetal heart rate
(FHR) increases from about 100 bpm at
5 weeks of gestation to 170 bpm at 10
weeks and then decreases to 155 bpm by
14 weeks. At 10–13+6 weeks, trisomy 13
and Turner syndrome are associated with
tachycardia, whereas in trisomy 18 and
triploidy there is fetal bradycardia (Figure
5; Liao et al 2001). In trisomy 21, there is
a mild increase in FHR.
Urinary bladder
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In first trimester
◦ >7mm=megacystitis
◦ 7-15 mm…..
◦ >15mm……