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Didascalia

At twelve weeks the fetus measure 6 cm.

A comprehensive study of all fetal structures can be done

NT + B-Test /Duotest/ Combined test

The examination of nuchal translucency, has an ultrasound and blood test components. In Italy this is known by various names: B test /bitest/duotest/integrated test etc..... This examination is carried in the first trimester of pregnancy.

The examination in the first trimester is the most important screening as it offers:

1) A DEFINED PERSONAL RISK FOR CHROMOSOMAL DEFECTS

Invasive procedures such as amniocentesis and chorionic villus sampling, offer a full diagnosis of chromosomal anomalies. However they carry risk of miscarriage or complications.

For 30 years the criterion used for identifying whether the risk of invasive procedure was justified was based only on maternal age, an evaluation which although necessary, was very generic and did not take into account individual biological differences. Today we have a method for identifying high risk pregnancies based on nuchal transluncency, which is 3 times more reliable

See below some examples:

-I am 36 years old and in order to have peace of mind, I have been advised to have an invesive procedurel... but this has a risk!

In deciding whether to do an invasive procedure, nuchal translucency (with nasal bone and blood test) is three times more reliable than the age related risk. Even at 40 years, a pregnant woman can have a low risk for chromosomal defects, if the fetal parameters and the mother’s biochemistry are normal.

  -I am 26 years old, I am doing well, I do not have history of chromosomal syndromes in my family or that of my spouse. Why would I need a test given that I have a very low risk...?

Because the low risk doesn’t mean anything. Chromosomal defects are accidents, which can occur regardless of maternal age. Most babies born with chromosomal defects, are born of women below the age of 35 (check here the reason). The nuchal translucency examination identifies most pregnancies with high risk. 

Comparison of results obtained based on criteria used for doing an invasive procedure.

 Chosen criteria for doing an aminio - chorionic villus sampling (cvs)

% pregnant women who have amnio -cvs

N. of invesive procedures made

Expected Complications
from amniocentesis

Expected miscarriages
from
amniocentesis

N. of Down diagnosed

Age:  at 35 years

20%

100.000

3.800

1.000

300(30%)

Age+NT+NB +Tr+blood test

2%

20.000

760

200

950(95%)

2) FETAL MORPHOLOGY SCAN AT 12 WEEKS

Fetal malformations, which are caused by errors in the process of organ formation or the fetus’s structure, are much more frequent than chromosomal defects. Previously the examination of fetal malformations could only be conducted at 20 weeks. At 12 weeks, the fetus is fully formed and therefore with the right equipments it is possible to do a morphology examination during the first trimester and the presence of most malformations will result in an increased nuchal translucency (see early morphology scan).

3) AN ESTIMATED RISK FOR PREGNANCY COMPLICATIONS

By combining the information obtained on the mother from the clinical history obtained with ultrasound scan (uterine artery), biophysical and biochemistry, it is possible to obtain an individual risk for a wide range of pregnancy related risks such as preterm delivery, diabetes and severe hypertension (early pre-eclampsia)

Last Edit: 05/08/2013 7:56pm
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