How much blood and stem cells does a typical umbilical cord hold?

When parents request cord blood collection, their birthing team tries their best to retrieve as much blood as possible from the umbilical cord. But the amount of blood that is left in the umbilical cord varies quite a bit between babies, and the amount of cord blood that is collected also depends on the skill of the collector and how long the cord clamping was delayed.

It might be helpful for parents to know that the median or typical volume of cord blood that is collected by family banks is only 60 mL or 2 ounces. That volume of cord blood corresponds to 470 million Total Nucleated Cells (TNC) or 1.8 million cells that test positive for the stem cell marker CD34. Thus, most full-term babies have over a million blood-forming stem cells for cord blood banking.

Parents should also be aware that public cord blood banks in the US and Europe will only keep collections that are much bigger than average, in the range of a billion TNC or 100 mL (3 ounces) in blood volume. When smaller collections are sent to public banks they are used for research or discarded.

The phrase "one cord blood unit", or CBU, refers to the full collection from a single baby.

Reference:
Sun, JJ et al., Transfusion 2010; 50(9):1980-1987. doi:10.1111/j.1537-2995.2010.02720.x