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Prenatal Test: Percutaneous Umbilical Blood Sampling (PUBS)

Medically reviewed by: Thinh Phu Nguyen, MD

What Is Percutaneous Umbilical Blood Sampling (PUBS)?

This quick test — also called cordocentesis, fetal blood sampling, or umbilical vein sampling — takes fetal blood directly from the umbilical cord. Doctors use it to check for disorders in the fetus.

PUBS isn't used as much as other diagnostic tests (such as amniocentesis and chorionic villus sampling), but may be done if results from those tests are not conclusive.

Why Is Percutaneous Umbilical Blood Sampling Done?

Percutaneous umbilical blood sampling usually is done along with an ultrasound and amniocentesis if a health care provider:

  • needs to quickly check a baby's chromosomes for problems
  • is concerned that the baby may have another problem, such as a low blood count, low platelet count, or a thyroid condition

The advantage to 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.

Should I Have Percutaneous Umbilical Blood Sampling?

Your health care provider may recommend this test if:

  • an abnormality was noted on an ultrasound
  • results from other tests aren't conclusive
  • Rh incompatibility might be an issue
  • the baby might have an infection (such as toxoplasmosis)

Risks are associated with PUBS, such as miscarriage or infection. Discuss the risks and benefits of this test with your health care provider.

What Happens During a Percutaneous Umbilical Blood Sampling?

This test takes a fetal blood sample by guiding a needle into the umbilical cord. A fine needle passes through the mother's abdomen and uterus into the umbilical cord, then the blood is withdrawn for testing.

When Are Percutaneous Umbilical Blood Samplings Done?

Percutaneous umbilical blood sampling usually is done after the 18th week of pregnancy.

When Are the Results Available?

PUBS results usually are ready within 3 days.

Medically reviewed by: Thinh Phu Nguyen, MD
Date reviewed: July 2022