Any pregnant woman wants to be sure that her baby is completely healthy. Women who have reason to doubt it especially need such confidence. You can find out the truth by agreeing to amniocentesis, chorionic biopsy, and cordocentesis. However, these procedures can be life-threatening for the child. Today there is a safer alternative, the DOT test.
What it is?
The DOT test is a non-invasive method for prenatal DNA diagnostics. It is designed to determine the sex of the child, as well as possible chromosomal pathologies, such as Down syndrome and a number of other anomalies. For the study, blood taken from a vein of a pregnant woman is used. There are no punctures of the fetal bladder and the associated risks of losing the baby.
The essence of the method is based on understanding the processes that take place in the body of the expectant mother during pregnancy. So, due to the natural death of some cells of the placenta, some of the blood cells of the fetus enters the mother's blood. By the 10th week of pregnancy, the amount of such free-circulating extracellular DNA of the baby in the mother's blood approaches 10% of the total amount of mother's blood.
From this time on, you can do the DOT test. In a blood sample taken from a woman's vein, fetal DNA is isolated. His research provides a detailed answer to the question of whether the baby is healthy. The test shows whether the crumbs in the mother's womb have pathologies such as:
- Down syndrome;
- Edwards syndrome;
- Patau syndrome;
- Klintfelter's syndrome;
- Turner syndrome.
All these anomalies are considered total, and often lethal for the baby, since they are not compatible with life. An exception is Down's syndrome: "sunny" babies are viable. But not every family is ready to accept and raise such a child. That is why there is a need for a DOT test.
Is the analysis accurate?
The veracity of the DOT test is quite high. Thus, he defines the Edwards, Patau and Down syndromes almost unmistakably: by 99.7%. Turner and Klinefelter syndromes - with a probability of up to 90%. The sex of the child is determined already at 10-11 weeks with a probability of more than 99%. With the same accuracy, the blood group and the Rh factor of the baby are determined, which makes it possible to assess the risks of developing the Rh conflict if a woman has Rh negative blood.
An error is excluded if the material for the study is collected correctly and the study itself is carried out in accordance with all strict criteria.
Indications
The test can be performed on any woman she wishes. A prerequisite is singleton pregnancy. If a woman is carrying twins or triplets, then one cannot vouch for the accuracy of the DNA test results. But this is general information, and direct indications for the DOT test are:
- the mother's age is over 35 years old (with age, the likelihood of chromosomal abnormalities increases);
- increased or high risks based on the results of universal screenings, which are carried out for pregnant women in the first and second trimester of pregnancy;
- the probability of giving birth to an unhealthy child due to unfavorable heredity, if there have already been cases of the birth of such babies in the family;
- history of miscarriages or missed pregnancies;
- closely related marriage or pregnancy resulting from incest.
The test can also be carried out during pregnancy with the help of assisted reproductive technologies (IVF), as well as in surrogacy.
Contraindications
The test is not performed if more than one fetus grows in a woman's womb, as well as with concomitant oncological diseases of the expectant mother. Also, the test will not give a reliable result if over the past six months the expectant mother received a blood transfusion.
How is the test done
The DOT test is done in three simple steps. On the appointed day, the woman needs to come to the clinic and take a routine blood test. Further, the baby's DNA is isolated and examined from it by the method of genomic sequencing. The final stage is the decoding of the data and the design of the risk probability for each of the determined chromosomal diseases. It is this conclusion that is given to a pregnant woman.
How long does the research take?
Like all non-invasive prenatal tests (NIPTs), the DOT test is not done quickly. It usually takes 10 to 12 days to get results. In some cases, specialists may need a little more time. It all depends on the workload of the laboratory and the sequence of studies in a given medical institution.
Sometimes, within the allotted time, specialists fail to isolate the DNA of the fetus. The woman is invited to donate blood again for a new study.
Pros and cons
The undoubted advantage of the DOT test is that the result can be obtained much earlier than with other diagnostic methods. If you make a test at 11 weeks of pregnancy, then after ten days the result will be known. The first screening, by comparison, is only carried out between 11 and 13 weeks, and its results will also have to wait. In addition, the accuracy of the DOT test is incomparably higher, because screening diagnostics is the most common calculation of probability and nothing more.
Early information leaves the pregnant woman with a choice: it is possible to have time to terminate the pregnancy if she makes such a decision (at her own request, this can be done before twelve weeks of pregnancy). If the test is done at a later date, then the woman will have to receive confirmation of the result from non-invasive diagnostics by passing the invasive one, because such tests are not yet a reason for doctors to issue a referral for termination of pregnancy on medical grounds.
To get this referral, you still need to do a chorionic biopsy or amniocentesis. This is precisely the relative disadvantage of the method.
On the other hand, the woman has no doubts. If the DOT test showed Down syndrome in a child and a woman does not want to give birth to such a baby, then she will go for invasive diagnostics without unnecessary fears. The accuracy of the test is high, but a negative DOT test means there is no need for invasive diagnostics, the baby is all right, even if the results of the screening test were disappointing. DOT test results are difficult to interpret in two ways or in ambiguity. In the conclusion, the name of the disease and the actual risk of its presence in percent are indicated. Normally, the results should be negative and the risks low.
No one has the right to force a woman to terminate a pregnancy if the child is sick. She may decide to leave the baby, and then the doctors will continue to manage the pregnancy, provide all the necessary medication and counseling support.
Another notable disadvantage of the DOT test is that such diagnostics are not yet widely used. Such analyzes are carried out only in medical genetic centers, specialized clinics. These are not in every small town, and therefore a woman will have to find the nearest clinic and go there for the analysis.
The number of diseases detected by the DOT test is significantly lower than the number of pathologies that can be detected during invasive diagnostics. Therefore, in the contract with the clinic, the woman will necessarily be shown a clause stating that good results do not guarantee the birth of a healthy child.
How much does it cost?
In different regions of Russia, the price may differ. It all depends on the medical institution. On average, the cost of conducting a DOT test as of the beginning of 2018 is 29 thousand rubles. The most affordable prices are offered by the Genoanalytica and UltraMed network clinics.
Reviews of pregnant women
Despite the fact that the test has been used in Russia for about 5 years, many women during pregnancy have no idea about this diagnostic method. Affected by the lack of reliable and detailed information, because doctors are in no hurry to talk about the new product, primarily because they may be suspected of imposing paid medical services. Another reason for the silence of obstetricians and gynecologists is the need to carry out invasive diagnostics anyway if the child has pathologies.
For these reasons, the number of reviews about the DOT test is very, very small. However, the available reviews make it possible to judge that the study is really accurate, albeit quite expensive. The women who found information, funds and made such a test were very pleased: whatever the truth, it is better than ignorance.
For the possibilities of the DOT test during pregnancy, see the following video.
