Nebojša Zečević

MOTHER`S BLOOD REVEALS GENETIC ABNORMALITIES

Date 30.10.2018 17:21

Geneticist Milica Filipovic Stanković explains how to safely and with certainty determine genetic abnormalities that may be a sign of Down, Edwards, Patau and other syndromes



- The main "culprit" for the falure to reduce the number of children born with chromosomal abnormalities is the unreliability of the tests used. The Geneticist Milica Filipovic Stanković explains that the majority of these children are born to women in the 20-35 age group, where prenatal diagnosis relies solely on double and triple tests.

What influences the occurrence of abnormalities?
- Some of the factors are part of the modern way of life such as high levels of stress, exposure to different forms of ionizing radiation, recent wars and conflicts along with the fact that the mothers`s age is increasing year on year. Pregnant women cannot avoid most of these factors. However, they can know whether their baby is carrying a genetic error in time. It should also be noted that the goal of diagnosis is not necessarily to reject the fetus with genetic abnormality, but, if needed, to provide parents with the opportunity to adequately prepare with the necessary professional help.

What are the most common genetic abnormalities that pregnant women are at a higher risk?
- The most common abnormalities are Down, Edwards, Patau, Tarner and Klinefelter syndrome. In over 90% of caes these abnormalities are the result of accidental events that can"t be linked to a specific cause, although older pregnant women are at a slightly higher risk than pregnant women whose families already have a child with a syndrome (eg Down). However, every woman is at risk of having a child with genetic disorders.

Is the number of children born with genetic abnormalities increasing in Serbia?
- Paradoxically, in our country, according to official data, most children with Down syndrome are born to women aged 25-35. Also, in Serbia over the last ten years, despite the increased number of invasive diagnostic procedures, the number of children born with Down syndrome is almost unchanged.

Statistics of The Institute of Public Health of Serbia "Dr Milan Jovanovi Batut


Can this statistic change?
- Pregnant women need to understand the importance of prenatal diagnosis, and the gynecologists must tell them about the existence and purpose of new genetic tests.

How can these abnormalities be diagnosed?
- In addition to ultrasound examination, which is a must, our hospitals are routinely performing combined screening in the first and second trimesters with the so-called double and triple tests. If the genetic consulting team finds that there is a justified need, invasive diagnostic procedures are also performed: amniocentesis, cordocentesis and biopsy of chorionic bumps.
In recent years, pregnant women in Serbia have had a new option in prenatal testing, a non-invasive prenatal test, which unfortunately has not yet been recognized by The National Health Insurance Fund and cannot be used in state hospitals.

What is included in non-invasive prenatal diagnosis?
- Non-invasive prenatal diagnostic procedures include all measures designed to detect genetic abnormalities including ultrasound examinations, combined biochemical screening of the first and second trimesters and available non-invasive prenatal genetic tests.

Often a double test is done. What is revealed by this test?
- Double tests or combined screening is performed between the 11th and 14th week of pregnancy, combining the mother"s age with the values of two parameters derived from the mother"s blood and nuchal translucency thickness of the fetus. Based on these data, it is calculated whether there are some of the most common chromosomal abnormalities in the fetus. However, this test is characterized by a high rate of false positive results (about 5%), which means, in practical terms, that out of 20 women who test positive on the double test, one will be carrying a child with Down syndrome. On the other hand, these tests are also characterized by a high rate of false negative results (about 15%), so out of 20 women carrying a baby with Down syndrome, up to 3 of them will test negative on the double test.
Thus, the double test has statistical value and a large number of pregnant women are refered for invasive diagnostic tests. In fact, only 3% of cases will confirm the presence of some chromosomal abnormalities.

Can there be less risk, with greater reliability, to determine the existence of anomalies?
- It can be done with the help of non-invasive prenatal tests (NIPTs) that are completely safe. It has been found that during pregnancy there is a certain percentage of free DNA from the fetus in the mother"s blood. This DNA from the baby can be isolated from a small sample of the mother"s venous blood, which can then tested for the most common genetic malformations.

When is the best non-invasive test to be done?
- Beginning of the 10th week of gestation, so that there is no risk of possible complications such as infection, contractions, bleeding or miscarriage. Approximately 10 milliliters of blood is taken from the mother"s veins and analysed. The extreme reliability and precision of this technology has been proven in a large number of clinical studies.


AMNIOCENTESIS


Amniocentesis is an invasive test

NIPT is a non-invasive test: no risk of miscarriage, infection or bleeding

NIPT is a non-invasive test: no risk of miscarriage, infection or bleeding


Who can recieve a non-invasive prenatal test?
Since it is not invasive and completely safe, it can be taken by all pregnant women who want to be sure they will not give birth to a child with one of the most common genetic disorders, those who have had a bad double / triple test or ultrasound in the first and second trimesters, and want to avoid the risk of invasive diagnostics, those who got pregnant through In vitro fertilisation, older pregnant women, and those who have a personal or family history of genetic disorders.
What does a non-invasive prenatal test reveal?
- A non-invasive prenatal test very early in pregnancy detects the presence of some of the most common genetic disorders in white population, such as Down syndrome, Patau"s syndrome, Edwards syndrome, sex chromosome abnormalities and six microdeletion syndromes. At the parents" request, the baby`s sex can be determined. According to all recent publications, the reliability of these non-invasive tests is almost perfect.
Can a non-invasive test replace amniocentesis?
- This test is not a substitute for amniocentesis, but it is a great way to avoid it. A positive finding from a non-invasive prenatal test should be verified by a confirmatory test, while negative findings suggest that only a continuation of normal pregnancy check-ups with gynecologist is advisable.
How does a pregnant woman choose a real test?
- The fact is that the number of available tests in our country is great and that pregnant women are often confused about how to decide.
In addition to the type of test or reputation of the lab, pregnant women should pay attention to the expertise of the medical staff in our country because these people are responsible for the validity of sampling and sample transport to the lab as well as later interpretation of the findings. Before taking the decision, pregnant women should consult her gynecologist and geneticist.
Tags: non-invasive prenatal test Down pregnancy syndrome risky pregnancy livia genetics



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Asst. Nebojša Zečević, MD, PhD, a specialist in Gynecology and Obstetrics and doctors of other medical specialties, advise on how to protect health, deal with medical problems and diseases and have healthy offspring.

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