Cordocentesis, or fetal blood sample, is a prenatal diagnostic test, carried out from 18 or 20 weeks of gestation, and consists of taking a sample of blood from the baby from the umbilical cord, to detect any chromosomal deficiency. in the baby, such as Down's 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.
When to do cordocentesis
The indications for cordocentesis include the diagnosis of Down syndrome, when it cannot be obtained through amniocentesis, when the ultrasound results are inconclusive.
Cordocentesis allows the study of DNA, karyotype and diseases such as:
- Blood disorders: 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 stunted, and to identify fetal hydrops, for example.
In addition, it is also very useful for the diagnosis that the baby has some congenital infection and can also be indicated as a form of treatment for intrauterine blood transfusion or when it is necessary to administer drugs to treat fetal diseases, for example.
Learn other tests for the diagnosis of Down Syndrome.
How cordocentesis is done
No preparation is necessary before the exam, however the woman must have done an ultrasound exam and a blood test prior to cordocentesis to indicate her blood type and HR factor. This exam can be performed at the clinic or hospital, as follows:
- The pregnant woman lies on her back; The doctor applies local anesthesia; With the help of ultrasound, the doctor inserts a needle more specifically in the place where the umbilical cord and placenta join; The doctor takes a small sample of blood from the baby with about 2 to 5 ml; the sample is taken to the laboratory for analysis.
During the examination, the pregnant woman may experience abdominal cramps and therefore should rest for 24 to 48 hours after the examination and not have intimate contact for 7 days after cordocentesis.
Symptoms such as fluid loss, vaginal bleeding, contractions, fever and pain in the belly may appear after the examination. For relief of pain and discomfort 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 so 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; Loss of blood at the place where the needle is inserted; Decreased baby's heart rate; Premature rupture of the membranes, which may favor premature delivery.
Generally, the doctor orders cordocentesis when a genetic syndrome or disease is suspected that has not been identified through amniocentesis or ultrasound.
