Cordocentesis (Umbilical Vein Sampling)

WHAT IS UMBILICAL VEIN SAMPLING?

Umbilical vein sampling also called “cordocentesis”, “fetal blood sampling”, or “percutaneous umbilical cord blood sampling (PUBS)”,  is a diagnostic genetic test that examines blood from the fetal umbilical cord to detect a fetal abnormality.

PURPOSE/USES

Umbilical vein sampling can be used to detect:

• Certain genetic disorders
• To detect and treat blood conditions, such as fetal anemia, rubella.
• To detect infections such as toxoplasmosis
• To deliver blood and medications to the fetus through the umbilical cord
• To check fetal chromosomes through chromosome microarray or karyotype analysis.

RISK

The use of cordocentesis is becoming rare due to the higher risk associated with it. Consequently, other diagnostic procedures such as amniocentesis and chorionic villus sampling, which pose a lower risk of fetal death, can be used instead for prenatal diagnosis of disease. Umbilical vein sampling carries a higher risk of complications to the baby including death. 

Potential serious risks include:

• Infections. 

Rarely, umbilical vein sampling can lead to a uterine or fetal infection.

• Fetal bleeding.  

From the area where the needle is inserted is a common and life-threatening complication.

• Slowing of the fetal heart rate.
• Cord hematoma. 

A collection of fetal blood within the cord might occur during or after umbilical vein sampling.

• Fetal-maternal bleeding

Fetal blood might end the mother’s circulation in about 40 percent of procedures. The problem is common when the placenta lies in the front of the uterus.

• Transfer of maternal infection. 

If the mother has certain infections, such as HIV, hepatitis B, Hepatitis C, they might be passed to the baby.

• Loss of pregnancy. 

PUBS carries a higher risk of fetal death than other prenatal diagnostic tests. The risk is about 1-2 percent for a fetus that appears normal and is being tested for genetic disorders.

ELIGIBLE CANDIDATES

Pregnant women who are on their 18 weeks or over of pregnancy.

HOW TO PREPARE FOR PUBS

• If you are 23 0r more weeks pregnant, you’ll be asked to avoid eating or drinking after midnight before umbilical vein sampling.
• Prepare to come with your partner or friend to the appointment for emotional support or to drive you home afterward.
• Before week 20 to 23 of pregnancy, the procedure is usually done in an outpatient facility or the doctors’ office.
• After week 23 of pregnancy, the procedure is usually done in the hospital, in case the baby develops complications that might require an emergency delivery.

THE UMBILICAL VEIN SAMPLING TECHNIQUE

The entire procedure generally lasts for 45 to 60 minutes.

Before The Procedure

• A sample of your blood will be taken for comparison with the fetal blood samples.

• You may be given specific instruction
• You may be  asked to change into a hospital gown
• You may be asked to lie on your back on the exam table
• You may be given antibiotics about 30 – 6minuteste before the procedure.

During The Procedure

• Ultrasound will be used to locate the umbilical cord in your uterus.
• A special gel will be applied to your belly
• Your baby’s position will be shown on a monitor guided by an ultrasound transducer.
• The health worker will clean your belly.
• Using ultrasound to guide the procedure, the doctor inserts a fine needle through your abdomen into the fetal vein in the umbilical cord.
• He withdrew a small amount of blood in the o syringe.
• And he removes the needle.

After The Procedure

• You will have a small discomfort or cramping temporarily.
• Your health worker will use an ultrasound or an extended labor monitor to track your baby’s heart rate after the procedure.
• As you return home, you may be asked to rest all through the remaining part of the day.
• You may likely be able to resume normal activities the next day. Call your doctor if you experience vaginal bleeding or fluid leakage.

RESULTS

The blood sample will be analyzed in a laboratory, and the test results will be available within 3 days. Your doctor or a genetic expert will help you understand the results of the test. If your test results are normal, your doctor will discuss the need for any follow-up appointment with you. If your baby has an infection, your doctor will discuss the treatment options with you. If your baby has severe anemia, the baby might receive blood transfusion through the umbilical cord.

If the test results show that your baby’s condition is not able to be treated, you might have to make a hard decision on whether to continue the pregnancy or not.

FAQs

• What does the s percutaneous umbilical blood sampling test stand for?

Percutaneous umbilical cord blood sampling [PUBS], also known as cordocentesis, fetal blood sampling, or umbilical vein sampling, is a diagnostic genetic test that examines blood from the fetal umbilical cord, to detect fetal abnormalities.

• How do you take a fetal blood sample?

After cleaning the mother’s abdomen with antiseptic, a long and thin needle is inserted into the mother’s uterus by ultrasound. Blood may be taken from blood vessels of the umbilical cord; this is also known as cordocentesis or percutaneous umbilical cord blood sampling [PUBS].

• At what stage of pregnancy is amniocentesis done?

Amniocentesis is usually carried out between the 15th and 20th weeks of pregnancy, but you can have it later, if necessary at all. It can be performed earlier, but this may increase the risk of complications of amniocentesis and is usually avoided.

• Do umbilical cords carry oxygenated blood?

The umbilical vein carries oxygenated, nutrient-rich blood from the placenta to the fetus, and the umbilical arteries carry deoxygenated, nutrient-depleted blood from the fetus to the placenta. Any impairment in blood flow within the cord can be a catastrophic event for the fetus.

• What is the advantage of fetal blood sampling?

The advantage of PUBS IS ITS SPEED. If the fetus might be anemic or have a platelet disorder, this test is the only way to confirm it because it uses a blood sample rather than an amniotic fluid sample. It also allows transfusion of blood or needed fluids into the baby, while the needle is in place.