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What is percutaneous umbilical blood sampling?

Percutaneous umbilical blood sampling (PUBS), also known as cordocentesis, is a diagnostic procedure used to evaluate many different kinds of fetal conditions.

PUBS is usually conducted after 18 to 19 completed weeks of pregnancy. During the procedure, a trained specialist uses ultrasound imaging to guide a needle through the maternal abdomen and into the umbilical cord where the sample of fetal blood can be taken.

After the procedure, the blood sample can be used to diagnose a wide spectrum of fetal conditions, ranging from infections to genetic disorders.

Our approach

If you are referred to our Center for Prenatal Diagnosis and Testing, a branch of our Division of Maternal Fetal Medicine, you will have access to cutting-edge technology and some of the best diagnostic equipment in the region. A team of physicians, sonographers and nurses will study your medical history, conduct an in depth evaluation and order the proper tests to make an accurate diagnosis.

Percutaneous umbilical blood sampling (PUBS) is a delicate procedure; it should always be performed by a highly trained physician. At Northwell Health, you will be cared for by a maternal fetal medicine specialist with extensive experience in conducting fetal procedures. You will also have access to state-of-the-art technology and a multidisciplinary team to offer excellent care every step of the way.

Why it's done

PUBS is used only when less invasive diagnostic procedures cannot provide conclusive results. In most cases, PUBS is used to diagnose blood conditions, like fetal anemia, though fetal infections and certain genetic conditions can also be diagnosed with a PUBS procedure.


Because PUBS is an invasive procedure, there are a handful of risks associated with the treatment, including:

  • Infection to the mother, baby or both
  • Fetal bleeding
  • Blood clots that may cause the baby’s heart rate to drop
  • Emergency cesarean section (C-section) in rare cases
  • Loss of pregnancy, though this occurs in less than 2 percent of procedures

Preparing for your appointment

Ahead of your PUBS procedure, you will be told not to eat or drink anything after midnight before your procedure. You may also receive steroid injections as a precaution. These injections help develop your baby’s lungs in case he or she needs to be delivered through an emergency C-section. This helps your baby reach viability, a stage of pregnancy in which the baby can survive outside of the womb. Antibiotics will be administered to reduce the risk of infection.

On the day of the procedure you will be offered optional local anesthesia. Your baby may also be given medicine to temporarily stop fetal movement during the procedure.

Because there is a risk of needing an emergency C-section, we take extra precautions to prepare as well. Your PUBS procedure will be conducted in close proximity to an operating room, and members of labor and delivery, anesthesiologists and neonatologists are made aware of the procedure. In the unlikely event you need an emergency delivery our team is ready.

What to expect after treatment

After the procedure is finished and the needle is removed, you will be monitored for several hours. It may take a few hours until you can feel your baby move again, as the medicine gradually wears off.

Once the medication has worn off, you will likely be discharged on the same day. You may feel cramping and soreness after the procedure.

A follow-up appointment is needed within the next few days to discuss the results. Additional treatment may be necessary depending on what is found from the fetal blood sample. Your physician will be able to walk you through your options and answer any questions you have.

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