Currently, only one time. Yes, private banking is incredably expensive. If you are having a baby, please consider donation to the public bank. It is free for the mother and will go to help someone else.
is the National Marrow Donors Program for the US and will tell you how to go about donating to the public banks. If you are in a different country, search for your country's marrow program or email me and I will find it for you.
The down side to public donation is that the majority of hospitals are not set up to receive public donations, so you will have to do the leg work and make plans for it ahead of time.
There are also restrictions on who can donate, simular to the restrictions for the marrow registery, since that is what cord blood is currently used for (it can be used in lieu of actual marrow in bone marrow transplants.)