Cord blood

Definition

Cord blood is a sample of blood collected from the umbilical cord at the time of birth.

How the test is performed

Immediately after the birth of your baby, the umbilical cord is clamped and cut. If cord blood is to be drawn, another clamp is placed 8 to 10 inches away from the first, then the isolated section is cut and a blood sample is collected into a specimen tube.

How to prepare for the test

No special preparation is necessary for this test.

How the test will feel

You will not feel anything beyond the normal birthing process.

Why the test is performed

Cord blood testing is done to determine the following:

• Bilirubin levels
• Blood culture (if an infection is suspected)
• Blood gases, to evaluate the oxygen, carbon dioxide, and pH levels
• Blood sugar level
• Blood type and Rh
• Complete blood count (CBC)
• Platelet count

Normal Values

Normal values mean that all items evaluated are within normal range.

What abnormal results mean

A low pH (less than 7.15) means there are high levels of acids in the baby's blood. This might occur when the baby does not get enough oxygen during labor. One reason for this could be that the umbilical cord was compressed during labor or delivery.

A blood culture that is positive for bacteria indicates septicemia.

High levels of blood sugar (glucose) in the cord blood may be found if the mother has diabetes. The newborn will be watched for hypoglycemia after delivery.

High levels of bilirubin could be due to:

• Congenital CMV
• Congenital hepatitis
• Congenital rubella
• Congenital toxoplasmosis
• Dubin-Johnson syndrome
• Jaundice in the mother
• Mother taking sulfa drugs during pregnancy
• Rh incompatibility

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What the risks are

There are no risks above and beyond those normally experienced by the mother and child at the time of birth.

Special considerations

Most hospitals routinely collect cord blood at birth, since it is relatively convenient and birth is the only time it is possible to do. Some parents choose to have cord blood banked, believing it might be useful later if the child has a condition that would require a bone marrow transplant. Cord blood banking for personal use is done by private companies, which charge for the service.

However, experts say that cord blood is rarely needed and often cannot be used because it contains the same cells that caused the disease in the child.

References

American Academy of Pediatrics Section on Hematology/Oncology, American Academy of Pediatrics Section on Allergy/Immunology, Lubin BH, Shearer WT. Cord blood banking for potential future transplantation. Pediatrics 2007;119(1):165-170.

Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007.