Diagnostic Tests 2022

Fetal sexing: what é, like é done and results

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Fetal sexing: what é, like é done and results
Fetal sexing: what é, like é done and results
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Fetal sexing is an exam that aims to identify the sex of the baby from the 8th week of pregnancy through the analysis of maternal blood, in which the search for fragments of the Y chromosome, which is present in the male.

This exam can be performed from the 8th week of pregnancy, however the more weeks you have of pregnancy, the greater the certainty of the result. To perform this exam, the pregnant woman does not need a medical recommendation and should not be fasting, it is even important that she is well fed and hydrated so she does not feel sick at the time of collection.

Although it is an exam with high sensitivity and effectiveness, it is important that the baby's sex is confirmed by ultrasound from the 13th week of pregnancy, because some factors can interfere with the result, such as insufficient amount of fetal DNA circulation and blood transfusion in which the donor is male, for example.

How the exam is done

The fetal sexing test is done from the analysis of a small blood sample that is taken from the woman, which is then sent to the laboratory for analysis. In the laboratory, fetal DNA fragments that are present in the mother's blood are evaluated, and the research is carried out using molecular techniques, such as PCR, for example, to identify the presence or absence of the SYR region, which is the region that contains the Y chromosome, which is present in boys.

It is recommended that the exam be performed from the 8th week of pregnancy onwards to be more certain about the result. However, although the sensitivity of this test is high, it is important that ultrasound is also performed, which from the 13th week onwards has similar efficacy.

Performing the fetal sexing exam does not require preparation, but it should not be performed by women who use heparin-based anticoagulants, for example, as it may result in an inconclusive result.

Pharmacy fetal sexing

Although there are fetal sexing tests that can be done at home, these tests do not have scientific proof of their effectiveness, do not explain in detail how they work and are not sold in pharmacies, being only found on websites. Thus, it is considered that the only ways to be sure about the baby's sex is by performing fetal sexing or ultrasound from the 13th week onwards.

How to understand the results

The result of the fetal sexing exam may take up to 10 days to be released, however, if requested urgently, the result can be released within 3 days. The exam aims to identify the presence or absence of the SYR region, which is the region that contains the Y chromosome. Thus, the two possible results of the exam are:

  • Absence of the SYR region, indicating that there is no Y chromosome and therefore is a girl;
  • Presence of the SYR region, indicating that it is a Y chromosome and therefore is a boy.

In the case of identical twins, if the result is negative for the Y chromosome, the mother will know that she is pregnant with only girls, while if Y is detected, the pregnancy is only with boys.

In the case of fraternal twins, in which there are two placentas, the presence of Y fragments indicates that one of the babies is male, but it is not possible to be sure about the other. However, the absence of Y indicates that both babies are female.

What can interfere with the result

Some factors can interfere with the result and lead to a false result, such as the insufficient amount of circulating fetal DNA at the time the collection was performed, which can cause the result to be a false- female, since fragments of the Y chromosome would not have been identified.

In addition, recent blood transfusion or organ transplantation in which the donor is male can also influence the result, and the test may indicate that the baby is a boy.

However, to prevent false or inconclusive results from being released, two samples are collected from the woman, as the test is performed twice for the same person. If it is noticed that the results were different in the repetitions, a new blood collection is requested two weeks after the first collection in order to have a more accurate result.

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