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Diagnostic Tests 2023

Cordocentesis: what é, when to do it and possible risks

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Cordocentesis: what é, when to do it and possible risks
Cordocentesis: what é, when to do it and possible risks

Cordocentesis, or fetal blood sample, is a prenatal diagnostic test, performed from 18 to 20 weeks of gestation, and consists of taking a sample of the baby's blood from the umbilical cord, to detect any chromosomal deficiency in the baby, such as Down Syndrome, or diseases such as toxoplasmosis, rubella, fetal anemia or cytomegalovirus, for example.

The main difference between cordocentesis and amniocentesis, which are 2 prenatal diagnostic tests, is that Cordocentesis analyzes the baby's umbilical cord blood, while Amniocentesis analyzes only the amniotic fluid. The karyotype result comes out in 2 or 3 days, which is one of the advantages over amniocentesis, which takes about 15 days.

Withdrawal of blood between the cord and placenta

Blood withdrawal between the cord and placenta

When to do cordocentesis

Indications for cordocentesis include the diagnosis of Down Syndrome, when it cannot be obtained through amniocentesis, when ultrasound results are inconclusive.

Cordocentesis allows the study of DNA, karyotype and diseases such as:

  • Blood diseases: Thalassemia and sickle cell anemia;
  • Blood clotting disorders: Hemophilia, Von Willebrand Disease, Autoimmune Thrombocytopenia, Thrombocytopenic Purpura;
  • Metabolic diseases such as Duchenne Muscular Dystrophy or Tay-Sachs Disease;
  • To identify why the baby is growth-restricted, and
  • To identify hydrops fetalis, for example.

In addition, it is also very useful for diagnosing that the baby has a congenital infection and can also be indicated as a form of treatment for intrauterine blood transfusion or when it is necessary to administer medication in the treatment of fetal diseases, for example.

Learn other tests for the diagnosis of Down Syndrome.

How cordocentesis is performed

No preparation is necessary before the exam, however, the woman must have had an ultrasound exam and a blood test before cordocentesis and a blood test to indicate her blood type and RH factor. This exam can be performed at the clinic or hospital, as follows:

  1. The pregnant woman lies on her back;
  2. The doctor applies local anesthesia;
  3. With the help of ultrasound, the doctor inserts a needle more specifically in the place where the umbilical cord and placenta join;
  4. The doctor takes a small sample of the baby's blood with about 2 to 5 ml;
  5. The sample is taken to the laboratory for analysis.

During the exam, the pregnant woman may experience abdominal cramps and therefore she should rest for 24 to 48 hours after the exam and not have intimate contact for 7 days after cordocentesis.

After the exam, symptoms such as fluid loss, vaginal bleeding, contractions, fever and pain in the lower part of the belly may appear. For pain and discomfort relief, it may be useful to take a Buscopan tablet, under medical advice.

What are the risks of cordocentesis

Cordocentesis is a safe procedure but it has risks, like any other invasive exam, and therefore the doctor only requests it when there are more advantages than risks for the mother or baby. The risks of cordocentesis are low and manageable, but include:

  • About 1 risk of miscarriage;
  • Blood loss where the needle is inserted;
  • Decreased baby's heartbeat;
  • Premature rupture of the membranes, which can favor premature birth.

Usually the doctor orders a cordocentesis when there is a suspicion of a genetic syndrome or disease that has not been identified through amniocentesis or ultrasound.

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