Prenatal diagnosis includes all possible methods of population diagnosis and screening, whereby it is possible to detect or rule out chromosomal, structural, genetic and functional abnormalities and fetal lesions. To achieve these goals, there are currently invasive and non-invasive methods available to the medical world from the first to third trimester of pregnancy.

Interventional diagnostic methods include:

• Chorionic villus sampling (CVS)
• Amniocentesis
• Fetal blood sampling
• Fetoscopy

Non-invasive methods on the other hand include:

• Ultrasound testing for the diagnosis of morphological abnormalities of the embryo, the detection of indicators of indicative chromosomal abnormalities and the monitoring of embryonic development.
• Search of the mother’s fetal cells or embryonic DNA (cell-free DNA)

When is CVS or amniocentesis appropriate?

Both are prenatal diagnostic methods and are recommended by the doctors when there is an increased risk of chromosomal

Both are prenatal diagnostic methods and are recommended by the doctors when there is an increased risk of chromosomal abnormalities such as DOWN syndrome, congenital abnormalities of the fetus, in cases of genetic abnormalities in the family, as well as for the diagnosis of conditions such as sickle cell anemia, Cystic fibrosis, metabolic diseases and infections.

CVS is mainly performed in the first trimester, up to the 15th week, while amniocentesis is performed after the 15th week of pregnancy.

What are the complications?

Randomised studies have shown that the rate of elimination after capture of trophoblast (CVS) is the same as fetal loss after amniocentesis of the second trimester. There is only one randomised study comparing the dangers of amniocentesis with women who did only ultrasound. According to this study (Tabor 1986) the rate of abortion after amniocentesis was 1% higher. For this reason, doctors mention that the risk of miscarriage due to having had prenatal diagnosis tests methods is 1%. Nevertheless , newer studies have lowered the rate to 1/1000.

Is the mother’s age indicative of amniocentesis?

Reproductive age over 35 years of age is NOT a sufficient indication of amniocentesis, since with it as indication we can only diagnose about 30% of DOWN embryos with falsely positive results of about 5%. So if we carry out an amniocentesis based only on the age of the mother, we would perform 140 amniocenteses to find one child with Down syndrome, or lose one normal fetus for every two Down-syndrome-embryos.

What is Cell Free DNA Test?

It has been discovered that a blood sample taken from the mother after the 10th week of pregnancy includes 10% of the fetal blood. In this way, we can now reliably detect the most frequent Trisomies (chromosomal abnormalities with more chromosomes than normal, such as Down syndrome, Edward’s syndrome and Patau syndrome) with detection rates of> 99%, 97% and 92%, respectively (Cell free DNA)

What are the benefits of this test?

Is it a diagnostic test?

Non-Invasive Prenatal Care is not a diagnostic method but a screening test with the highest accuracy so far, compared to the conventional prenatal combination of 1^st and 2^nd trimester.

To which women is the test applicable?

This test can be applied to pregnant women, proposed as an option for the couple who would want a harmless test to reassure them that their fetus is well, excluding 97% of the most common chromosomal abnormalities (Tue 21, 18, 13)

How is the test performed?

An ultrasound examination of the fetus is always required to record fetal cardiac function and block structural abnormalities. Immediately afterwards we take some blood from the mother and send it to the relevant foreign laboratory safely.

When can the cell free DNA test be performed?

The test is proposed to be carried out from 10 to 32 weeks of gestation, with optimal gestational age at week 12 during cervical length measurement examination, so that the couple knows early the results, as well as the recombinant final risk for chromosomal abnormalities.

When do we expect to have the results?

The results from the test are usually ready after 10 to 15 days and the couple gets immediately informed via phone call.

Is there always a result?

In 2% of the cases there is no result from the test and this is due to a technical error in the analysis of the sample (eg a small percentage of detection of a fetal blood fraction in the mother’s blood). In this case we call the couple to repeat the test FREE and we expect the new results, which we will have at a statistical probability of 50%, due to a previous failure of the analysis.

How are the results interpreted? What are the new data for the correct interpretation of the result?

The result we get is low risk (good result) or increased risk (bad result).

The low-risk result means that the risk of chromosomal abnormalities from the examination of nuchal translucency decreases even further in relation to the fetal fraction% of fetal blood. So we know now how important the percentage of fetal blood recorded in the result is, as well as the initial risk that the pregnant woman has from examining cervical translucency.

The greater the fetal fraction gets, the greater the risk reduction is becoming, with the maximum reduction being noted with fetal fraction> 9%.

It is a screening test and not a diagnostic test.

Therefore, in the case of increased risk, a diagnostic test (amniocentesis, CVS) is required to verify the result.

It is NOT recommended to identify gender abnormalities and microdefects from the test as there are many false positive results, and there are no documented studies and safe methodology.

Are any additional tests / ultrasounds needed?

The cell-free DNA test does not provide information about other rare chromosomal abnormalities. If the ultrasound at 11-14 weeks shows an elevated neural transparency (more than 3.5mm) or major structural abnormalities in the embryo such as emphysema, holoprosencephaly, heart or megacity abnormalities, then the risk for some rare chromosomal abnormalities becomes high. In such cases, a diagnostic test (amniocentesis, CVS) is recommended.

The cell free DNA test does not provide information about structural abnormalities of the fetus, such as heart or brain abnormalities and spina bifida or information on fetal development. Therefore, it is advisable to have ultrasounds at 12 weeks, 20-22 weeks to look at fetal anatomy and at 32 weeks to evaluate fetal development.