Frequently Asked Questions


Collecting Cord Blood

How is cord blood collected?
It literally only takes minutes to save the stem cells in cord blood.  Once the cord is clamped, the cord is wiped with antiseptic and a needle is inserted into one of the veins in the umbilical cord to withdraw a few ounces of blood.

There are two methods of collection in common use.  One is to hang a blood bag lower than the mother and let gravity draw blood down the tube into the bag.  This method is used in most countries of the world, because it has the fewest steps, and therefore the fewest opportunities for mistakes or contamination.

The second method is to actively draw the blood out, just like when a person has a blood draw for a medical test.  The draw can be done with a standard syringe or with a bulb in the bag tubing that creates suction.  Studies have shown that actively drawing the blood will collect a larger volume faster.
How much blood and stem cells does a typical umbilical cord hold?
The median size of cord blood collections in family banks is 60mL or 2 ounces.  That small volume of liquid corresponds to 470 million Total Nucleated Cells (TNC) or 1.8 million cells that test positive for the stem cell marker CD34.  Thus, most healthy full-term babies have over a million blood-forming stem cells in their umbilical cord blood.   By comparison, most public cord blood banks will only keep collections that are much bigger than average, and throw out the donations that are below a threshold of a billion TNC, corresponding to a blood volume of about 90-100 mL or 3 ounces.

Sun, JJ et al., Transfusion Sept. 2010; 50(9):1980-1987
What questions should parents ask a Family Bank about collecting cord blood?
  • What instructional tools are provided for the physician and delivery staff?
  • Will the cord blood company actively contact the labor and delivery staff for you -- or are parents responsible for keeping them informed and coordinated?  
  •  What collection method do they use: gravity drip or blood draw?
  • Is the collection blood bag sterile, both inside and out, so that it can be used in the operating room for a C-section?
  • Do they provide the option of collecting additional stem cells from the placenta or tissue of the umbilical cord?
What are the most important things to do when collecting cord blood?
1. Read the instructions on the kit!  Too many healthcare providers think that they don't need to read and follow instructions.
2.  Sterilize before every needle stick.  When in doubt, sterilize again!
3. Volume, volume, volume.  You want to "milk the cord" for as much blood as possible.  If the blood vessel you are using stops working, try another or move upstream, but sterilize first.
How much cord blood is needed for a transplant?
The crucial thing is not the volume of the cord blood collection, but the number of stem cells it contains. Transplant doctors develop recommendations based on the Total Nucleated Cell count, or TNC, because it is the easiest measure to reproduce between different labs.    For treating cancer, the transplant dose should be at least 25 million TNC per kilogram of patient body weight (1 kilogram equals 2.2 pounds).  The average cord blood collection holds 8.6 million TNC per mL.  Thus, the optimal transplant dose requires harvesting:
1.3 mL of cord blood for every pound of patient weight, -or-
2.9 mL of cord blood for every kg of patient weight

However, as more transplant centers are adopting the practice of giving adult  patients "double cord blood transplants" with two cord blood units, it is less critical for both units to have adequate cell dose.

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What is delayed cord clamping?
Some people feel that the blood in the umbilical cord should be allowed to flow into the baby and that the cord should not be clamped while it is still pulsing.  Medical studies have shown that, particularly in parts of the world with poor infant health care, delayed cord clamping can help protect the baby from anemia (low blood counts) during the first 6 months of life.  However, a prolonged delay will allow the blood in the cord to clot, and the opportunity to collect the blood for stem cells will be lost.  Therefore, if clamping is delayed, it should not be more than two minutes.

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