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Prenatal Test: Percutaneous Umbilical Blood Sampling (PUBS)

Reviewed by: Armando Fuentes, MD

What Is Percutaneous Umbilical Blood Sampling (PUBS)?

This quick test — also called cordocentesis, fetal blood sampling, or umbilical vein sampling — examines fetal blood directly from the umbilical cord. It's used to detect disorders in the fetus.

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

Why Is Percutaneous Umbilical Blood Sampling Done?

Percutaneous umbilical blood sampling usually is done in addition to an ultrasound and amniocentesis if a health care provider:

  • needs to quickly check a baby's chromosomes for defects or disorders
  • is concerned that the baby may have another problem, such as a 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 with your health care provider if you choose to have this test.

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 A fine needle is passed through the abdomen and uterus into the umbilical cord, then the blood is withdrawn for testing.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.

Reviewed by: Armando Fuentes, MD
Date reviewed: August 2018