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    Gender Blood Test: Benefits of Prenatal Genetic Testing Explained

    Updated 04 November 2020 |
    Published 30 April 2020
    Fact Checked
    Reviewed by Eugenia Tikhonovich, MD, Obstetrician-Gynecologist, Medical Consultant
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    A blood test to determine the gender of your baby can also indicate the possibility of genetic disorders. Check all the pros of prenatal blood testing in this article.

    What is an early sex blood test?

    Prenatal genetic tests may provide information to would-be parents about the chances of their fetus having genetic abnormalities. There are two main kinds of prenatal genetic testing:

    • Screening
    • Diagnostic

    Prenatal screening testing may identify the likelihood of your baby having defects at birth (many among these are genetic abnormalities). These tests are:

    • Blood tests
    • Prenatal screening for cell-free DNA
    • A specific type of ultrasound

    Health care providers usually perform a prenatal screening test during the first or second trimester. Screening tests don’t definitively diagnose birth defects — if the results of the test indicate an increased risk of a genetic disorder, additional diagnostic tests may be needed to confirm a diagnosis.

    An early sex blood test is a non-invasive prenatal test (NIPT) during which a health care provider takes a blood sample to identify the sex of the fetus. This method analyzes the cell-free fetal DNA present in the blood during early pregnancy. 

    Cell-free fetal DNA is the small quantity of DNA the placenta releases into the maternal bloodstream during pregnancy. The doctor may screen the cell-free fetal DNA for a wide variety of genetic disorders, including Down syndrome, Edwards syndrome, Patau syndrome, trisomy 13, and problems related to the number of sex chromosomes. An early sex blood test is usually done at the beginning of week 10 of pregnancy. It may take about one week for the results to come back. Your doctor will recommend a diagnostic test such as chorionic villus sampling (CVS) or amniocentesis if your cell-free fetal DNA test comes back positive for a genetic abnormality.

    Why do a gender blood test?

    One reason for a blood test is to avoid invasive prenatal testing in the case of a female baby.

    The majority of the sex-linked disorders are recessive disorders linked to the X chromosome and are manifested exclusively in males as they contain only a single X chromosome. According to estimates, the X-linked recessive disorders may occur in around 5 out of 10,000 babies.

    Non-invasive prenatal testing (NIPT) is adopted nowadays in health care systems in many countries worldwide. The aim of a blood test for baby sex determination is to decrease the total number of invasive prenatal tests since doctors refer only those pregnant with a male fetus (according to the result of a sex blood test) for invasive testing.

    NIPT or invasive tests?

    Second trimester prenatal screening may include several blood or urine tests called multiple markers. These markers provide information about the risk of having a baby with certain genetic conditions or birth defects. The multiple markers include maternal serum AFP and maternal blood or urine estriol, inhibin, and human chorionic gonadotropin. Abnormal test results of AFP and other markers may mean that additional testing is needed. Since multiple marker screening is not diagnostic, it is not 100 percent accurate. It helps determine who should be offered additional (sometimes invasive) testing during pregnancy.

    Family planning

    If you have a family health history that includes a previous pregnancy or child with a genetic disease or birth defect, you might be more likely to have a baby with this condition. Learning more about your family health history before you get pregnant can give you time to address any concerns. Remember to consider the family health history of both potential parents. Be sure to discuss any concerns with your health care provider.

    Examples of genetic disorders that can be diagnosed before birth include cystic fibrosis, Duchenne muscular dystrophy, hemophilia A (which is inherited in an X-linked recessive manner), polycystic kidney disease, sickle cell disease, and Tay-Sachs disease.

    You may find it helpful to think about how you’ll use your blood test results in your care during pregnancy. Some couples want to know whether their baby will be born with any type of genetic disorder or not. With this knowledge, they get time to learn more about the genetic disorder so they can plan for the care of their child. In certain circumstances, some couples may make a decision to terminate the pregnancy.

    Genetic disorders

    A baby gender blood test or prenatal screening test helps determine the possibility of a fetus having certain genetic disorders. If a prenatal screening test indicates the possibility of a problem, a prenatal invasive diagnostic test such as CVS or amniocentesis may be performed.

    Amniocentesis is a type of prenatal diagnostic test that is usually done between pregnancy weeks 15 and 20. A very thin needle under ultrasound guidance withdraws a small quantity of amniotic fluid. It may take between one day and several weeks to get the results of the test.

    In chorionic villus sampling, a sample of placental tissue is taken to be analyzed for the presence of genetic disorders. CVS is usually done between pregnancy weeks 10 and 13.

    The analysis of the cells during prenatal diagnostic testing is done as follows:

    • Karyotype: This involves taking an image of the chromosomes and then arranging them from the largest chromosome to the smallest chromosome. It may help in detecting damaged, missing, or extra chromosomes.
    • Fluorescence in situ hybridization (FISH): This is a technique that may help in detecting common abnormalities in the number of chromosomes involving sex chromosomes and chromosomes 21, 18, and 13.
    • Chromosome microarray analysis: This may help in finding certain chromosomal disorders that karyotyping may miss.
    • DNA testing: You may ask for a specific genetic mutation test if you or your partner are carriers of certain specific genetic disorders.

    Were there cases when a gender blood test was wrong?

    Prenatal screening isn’t flawless. The rate at which inaccurate results occur varies for different tests. The only certain method for identifying the sex of the fetus is to undergo invasive prenatal testing, including amniocentesis and CVS.

    When do you need a blood test to find out the sex of your baby?

    A blood test to determine the sex of a baby may be useful in identifying fetuses who are at an increased risk of developing severe genetic diseases (recessive disorders linked to X chromosome) in pregnant people who have either delivered a baby with a recessive disorder linked to X chromosome or are carriers of these disorders.

    The outlook

    Non-invasive prenatal screening tests analyze the blood of a pregnant person to determine the likelihood of the presence of certain genetic disorders in their fetus. Small quantities of cell-free DNA of the fetus are present in the blood of a pregnant person during pregnancy. However, following delivery, this DNA leaves their bodies rapidly. These tests often eliminate the requirement for invasive prenatal diagnostic tests such as amniocentesis and CVS, thereby reducing the psychological and medical risks associated with them.

    History of updates

    Current version (04 November 2020)

    Reviewed by Eugenia Tikhonovich, MD, Obstetrician-Gynecologist, Medical Consultant

    Published (30 April 2020)

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