Cord blood

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 performed to assess the following:

  • Blood gases, to evaluate the oxygen, carbon dioxide, and pH levels  
  • Blood type and Rh  
  • Respiratory status  
  • Complete blood count (CBC)  
  • Platelet count  
  • Hemoglobin levels (Hgb)  
  • Hematocrit (HCT)  
  • Bilirubin levels  
  • Glucose  
  • Blood culture (if an infection is suspected)

Normal Values 
Normal values indicate that all items evaluated are within normal range.

What abnormal results mean 

A low pH (less than 7.2) indicates 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 delivery.

A blood culture that is positive for bacteria indicates septicemia.

Elevated levels of glucose in the cord blood may be found if the mother has diabetes. The newborn will be watched for rebound hypoglycemia after delivery.

Elevate bilirubin could indicate:

  • Maternal jaundice  
  • Maternal ingestion of sulfa drugs during pregnancy  
  • Rh incompatibility  
  • Dubin-Johnson syndrome  
  • Congenital toxoplasmosis  
  • Congenital rubella  
  • Congenital hepatitis  
  • Congenital CMV

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, because it can be used later if the child has a condition that would require a bone marrow transplant. Cord blood can be used to re-constitute the immune system in place of a transplant and doesn’t require a search for a compatible donor.

If your child has a normal and uneventful birth, your health care provider may choose to run selected tests on the sample and not bank the sample.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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