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Introduction ⬇

Percutaneous umbilical blood sampling (PUBS), also known as cordocentesis or fetal blood sampling, is a rarely used diagnostic procedure in which fetal blood is drawn from the vein in the umbilical cord. PUBS may be used if ultrasound, amniocentesis, and CVS do not provide adequate information about the fetus. PUBS has somewhat replaced fetoscopy because of the risk factors associated with the latter test. PUBS is usually performed after 18 weeks gestation and is probably a safer and easier way to sample blood from the umbilical cord of the fetus in utero. Fetal blood can be examined for hemophilia, hemoglobinopathies, fetal infections, chromosomal abnormalities, fetal distress, fetal drug levels, and other blood studies. Other common indications include rapid karyotype evaluation, fetal platelet abnormalities, and fetal growth restriction.

Procedure ⬆ ⬇

  1. Scan the maternal abdomen with a real-time ultrasound transducer (placed into a sterile glove) to provide landmarks as a 20- to 25-gauge spinal needle is first inserted and then guided into the fetal umbilical vein, 1–2 cm from the cord insertion site on the placenta.

  2. Aspirate the fetal blood sample into a syringe containing anticoagulant to prevent clotting of the sample.

Procedural Alert

Risks include transient fetal bradycardia, maternal infection, premature labor, and a 1%–2% incidence of fetal loss

Clinical Implications ⬆ ⬇

Abnormal blood results may reveal:

  1. Hemoglobinopathies

  2. Hemophilia A or B; other coagulation disorders

  3. Fetal infection

  4. Chromosome abnormalities, genetic diseases

  5. Isoimmunization

  6. Metabolic disorders

  7. Fetal hypoxia

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the procedure and its purpose, benefits, and risks. Obtain a properly signed and witnessed consent form.

  2. Assist with relaxation exercises during the procedure. Antibiotics may be given before the test to prevent infection.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Monitor maternal vital signs and perform external fetal monitoring or an NST. Observe for signs of fetal distress.

  2. Perform an ultrasound 1 hour after the procedure to ensure that there is no bleeding at the puncture site.

  3. Review test results; report and record findings. Modify the nursing care plan as needed.

  4. Counsel the patient appropriately about fetal therapy (e.g., red blood cell and platelet transfusion and drug treatment).

  5. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Reference Values ⬆

Normal