Cordocentesis , also called percutaneous cord blood sampling , is a prenatal diagnostic test performed during pregnancy to analyze the baby’s genetic information.
With this procedure, in addition to being able to investigate or diagnose different fetal diseases such as coagulation disorders, genetic diseases, infectious diseases, etc., it also serves as a way to carry out therapeutic actions such as transfusions or the administration of drugs.
It is an intervention that is used less and less frequently, since there are other somewhat less risky procedures, such as amniocentesis and chorionic villus sampling , with which it is possible to obtain a diagnosis of diseases in the fetus.
What is cordocentesis?
This test consists of puncturing a vessel from the fetus’s umbilical cord to extract a 3 to 5 ml blood sample for diagnostic and/or therapeutic purposes.
Previously, an ultrasound assessment of the size and position of the fetus , amniotic fluid and placenta is performed, then a puncture is performed to extract a small amount of blood for analysis.
What is it for?
It is used to study chromosomes or genes in fetal cells, when there is suspicion of infection, anemia or other fetal diseases, or to perform other tests on the blood of the fetus.
It also serves as an access route to perform some treatments inside the uterus.
Therefore, its indications are:
- genetic studies
- When a fetal anomaly is observed on ultrasound .
- To confirm amniocentesis results if the amniotic fluid sample is insufficient or the amniocentesis result is mosaicism.
- When the fetus has accumulation of fluid in the body (hydrops fetalis).
- When the fetus is not growing properly and the amount of amniotic fluid has decreased .
- Fetal CMV infection markers (platelets and liver profile)
- When fetal anemia is suspected .
- When fetal thrombocytopenia is suspected.
When and how is cordocentesis performed?
It is usually performed after 17-18 weeks of gestation . Maternal and sometimes fetal local anesthesia may be required.
The technique begins with the location by ultrasound of the placenta and the umbilical cord of the fetus that reaches it.
Once located and with the help of ultrasound to guide the needle, the puncture is made through the wall of the mother’s abdomen and uterus, to reach a vessel in the umbilical cord and obtain fetal blood.
What will I feel?
It can cause discomfort during the puncture and occasionally small bleeding from the umbilical cord that usually subsides in 1-2 minutes.
If there is abundant vaginal bleeding, loss of fluid or fever, the pregnant woman should go to the hospital emergency room.
The results have a reliability of more than 99%.
What risks does the test have?
Most of the time, the intervention does not cause harm or undesirable side effects. But being an invasive test, it has its risks for both the mother and the baby, although they are not frequent:
The most common risk is bleeding from the puncture site, which usually subsides in 1-2 minutes.
The most serious and less frequent risks are:
- Miscarriage or pregnancy loss (2-3% risk).
- Loss of amniotic fluid due to premature rupture of the bag or infection.
- Premature labor .
- Rh sensitization . When the blood cells of the mother and the fetus are incompatible, treatment is given to prevent it in susceptible cases.
- Hematoma at the puncture site (1 to 3 out of 100 women). It can be serious, producing fetal bradycardia and death within minutes if it compresses the cord.
- Fetal death after 28 weeks (1 in 100 women).
- Maternal infection (1 in 100 women) or peritonitis in extremely rare cases.
In addition, you must know that there are personal circumstances that can complicate the procedure and should be assessed by the doctor, such as: possible allergies to medications, coagulation disorders, illnesses, current medications or any other circumstance even if you do not consider it relevant.