1st Trimester screening

NT+ screening  (NT + biochemical screening in the 1st-trimester)

The test to estimate the Down syndrome risk



Assurance through knowledge and information

Being informed is an important part of prenatal care. We strive for the highest level of parental knowledge of modern diagnostic methods. Only well informed parents can make the right decisions and choose the most appropriate approach to prenatal diagnostics.


What are chromosomes?

Our body is composed of cells. Every cell contains identical genetic information. This information resides within the cell core in a structure called chromosome. The chromosomes are helical strands of DNA (deoxyribonucleic acid) that carry the genetic code. Every human cell, with the exception of the sperm and the egg, contains 46 chromosomes.


What is meant by chromosomal aberration?

Sometimes human cells contain a different number of chromosomes, or these chromosomes have a different structure. This disorder occurs at the beginning of the individual’s existence, at the moment of conception when the sperm fuses with the egg. There is a total of about 100 known syndromes. One of the most commonly known, and the most frequently occurring, is Down syndrome. 


What is Down syndrome?

Down syndrome is a chromosomal aberration where the cells have a redundant 21st chromosome. Consequently, the cells contain 47 chromosomes instead of 46. This disorder affects the intellect and is often accompanied by some congenital developmental defects. 


Which parents have a higher risk of having a child with the Down syndrome?

Any woman may have a child with Down syndrome, but the risk increases with the parents‘ age. At the age of 20, the risk is 1:600, but it rises to 1:5 for parents in their fifties. The majority of these cases is not related to occurrence within the family and is purely accidental — de novo.    


What is the NT screening + biochemical screening in the 1st trimester?

This test combines a sonographic measurement of the thickness of nuchal translucency (NT) with the analysis of mother’s blood. The test is done in the 11th-13th week of pregnancy. The combination of these two methods enables the detection of 75-80% of children with Down syndrome. The traditional screening done in the 16th week (the so-called triple screen test) can identify only 50-60% of children with this syndrome.

What are the advantages of the NT screening+……  ?

– high reliability with minimal risk

– accurate determination of pregnancy stage and delivery date

– diagnosis of multiple pregnancy

– timely detection of larger foetal malformations

How is the NT examination performed?  

The nuchal translucence (NT) test is done in the 11th-13th week of pregnancy. It sonographically measures the subcutaneous accumulation of fluid in the neck area of the foetus. Ultrasound shows this fluid as translucent. The presence of a larger amount of fluid in this area is often associated with chromosomal aberration, such as the Down syndrome. Examination through the abdominal wall is usually feasible. 


What is examined by the blood analysis?

The blood analysis consists of testing for two substances (PAPP and HCG), which originate in the placenta and pass into the mother’s blood. Pregnancies with Down syndrome exhibit abnormally high levels of these substances.


Will anything else be examined?

Yes, in addition to standard testing, we also focus on the presence of a nasal bone (NB) and on the flow pattern in the ductus venosus. Also, the test should be able to rule out recognizable morphological abnormalities (more under „Results“).


When should the sampling be done?

The sampling should be done between the weeks 11+0 and 13+5  of pregnancy (counted from the first day of the last menses or the known day of conception (e.g. the day of oocyte aspiration in the case of IVF) + 2 weeks. 


Calculation of the risk:

The calculation combines the known risk factors given by the mother’s age, the thickness of nuchal translucency, and the level of substances in blood. The result is a number indicating the risk of bearing a child with Down syndrome.


When will be the result known ?

The test result is available immediately after the evaluation and we relate it by telephone on the day of sampling. It is also ready for downloading on the same day on our site (www. prenatal.cz) under a specific password.


If the test result is negative….

If the calculated risk is lower than 1:300 (i.e. one affected child in 350, 1000, 15000…) the risk of having a child with Down syndrome in this pregnancy is low. It is important to realize that low risk does mean the same thing as no risk. Even with a negative result, it is still advisable to undergo a sonographic examination in the 20th week specifically intended to identify any possible congenital development defects in the foetus. 


If the test result is positive…

A risk ratio greater than 1:300 (i.e. one affected child in 10, 150, 280) indicates a greater probability of having a child with Down syndrome. This of course DOES NOT MEAN that the child actually has Down syndrome. The test result will be explained to you. If you wish, the possibility of this syndrome can be completely eliminated by genetic testing of the foetus (sampling the amniotic fluid or chlorionic villi). 


Is this examination covered by public health insurance?

According to the recommendation of Czech Gynecological Society, this examination is considered above-standard and is not covered by health insurance.