Amniocentesis: what is it and how is this diagnostic test done

Pregnancy and gestation are very delicate stages, because in this biological process the new organism begins to develop. This is why from a medical point of view it is important know as much as possible about what is going on in the developing fetus, Be able to intervene as quickly as possible in the event of a congenital disease.

Amniocentesis is the procedure doctors do to get this initial information and be able to make an early diagnosis during pregnancy. Throughout this article, we’ll go over everything you need to know about this test: what is amniocentesis, what are its functions, how it is performed, and what are the risks to consider.

    What is an amniocentesis?

    We call it amniocentesis a type of prenatal test in which an early diagnosis occurs through a medical procedure chromosomal diseases and fetal infections and secondarily it also helps us to know what the sex of the baby is before birth.

    To understand how it works, you must first know that throughout gestation the fetus is surrounded by a substance called amniotic fluid, The composition contains fetal cells. From the observation of this fact, the scientific community applied to the clinical field has discovered that the amniotic fluid is able to give us useful information about the health of the baby months before birth. Amniocentesis focuses on the analysis of this substance and its components.

    During amniocentesis, a small sample of amniotic fluid is obtained using a needle that is inserted into the woman’s abdomen at the same time that an ultrasound is done with which the process can be monitored. Second, the obtained amniotic fluid sample is analyzed in the laboratory, in which background the fetal DNA is studied to see if it contains genetic abnormalities.

    In which cases is it carried out?

    This prenatal test is only offered to women who are at significant risk of genetic disease. In most cases, the main reason for an amniocentesis is whether the fetus has chromosomal or genetic abnormalities that can occur in Down syndrome. As a rule, this diagnostic procedure is expected between weeks 15-18 of gestation.

    Therefore, it is not always necessary to do this, in most cases it is carried out only on pregnant women, in whom the baby is at risk of developing a genetic pathology. The reason it’s not for all women is because it’s a fairly invasive test that carries a low risk of miscarriage.

    Amniocentesis is associated with certain risks, a complete anatomical ultrasound is performed before performing it, in order to detect abnormalities in the baby. In cases where there is reason to suspect the existence of genetic or chromosomal alterations, An amniocentesis will be performed.

    Functions of this test: what is it for?

    The main cases in which amniocentesis is required include:

    • A family history of birth defects.
    • Abnormal results in ultrasound tests.
    • Pregnant women or children in whom she has had birth or gestation disorders.

    Unfortunately, amniocentesis fails to detect all possible existing birth defects. However, the ultrasound test done at the same time can detect birth defects that cannot be reported in amniocentesis such as cleft lip, heart defects, beam palate, or clubfoot.

    However, the risk that some congenital anomalies will not be detected by either of the two diagnostic tests cannot be excluded. Usually, the main diseases detected by amniocentesis son:

    • Muscular dystrophy.

    • Cystic fibrosis.
    • Sickle cell anemia.
    • Down’s syndrome.

    • Neural tube changes, As in spina bifida.
    • Tay-Sachs disease and related.

    Finally, the accuracy of amniocentesis is around 99.4%, so although it has some dangers, it is very useful in cases where there is a real suspicion of fetal abnormality.

    How do doctors do it?

    After cleaning the area of ​​the abdomen where the needle will be inserted with an antiseptic and administering a local anesthetic to relieve the stinging pain, the medical team locates the position of the fetus and placenta using an ultrasound scan. . Jokingly through these images, a very fine needle is inserted through the mother’s abdominal wall, The lining of the uterus and the amniotic sac, trying to push the end away from the fetus.

    A small amount of liquid, about 20 ml, is then extracted, and this sample is sent to the laboratory where the analysis will be carried out. In this space, the fetal cells are separated from the other elements present in the amniotic fluid.

    These cells are cultured, fixed and stained so that they can be observed correctly under a microscope. like that, chromosomes are examined for abnormalities.

    As for the baby and its environment, the puncture seals and the fluid in the amniotic sac regenerate over the next 24 to 48 hours. The mother should come home and rest for the rest of the day, avoiding exercise. In a few days, you will be able to resume a normal life unless your doctor tells you otherwise.

    the risks

    Although medical safety measures have made great strides in this area as well, amniocentesis is always a risk. The risk of miscarriage is most noticeable, although it only occurs in 1% of cases.

    The possibility of premature birth, injuries and malformations in the fetus is also an aspect to consider.

    Bibliographical references:

    • Carlson, LM and Vora, NL (2017). Prenatal diagnosis: diagnostic and detection tools. North American Obstetrics and Gynecology Clinics, 44 (2): 245-256.
    • Then, JW (2004). Diagnosis of amniocentesis in the middle of the trimester: to what extent ?. American Journal of Obstetrics and Gynecology, 191 (2): 607-15.
    • Underwood, M. A, Gilbert, W. M, Sherman, MP (2005). “Amniotic fluid: not just fetal urine anymore.” Journal of Perinatology. 25 (5): pages 341 to 348.

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