All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The blood is impure and it is not permissible to use it as a medicine unless there is a necessity. Therefore, it is not permissible to donate cord blood but if it is confirmed that it is beneficial in treating some diseases and it becomes a necessary means for treatment in a way that there is no other alternative, then it is permissible to be treated with it, and in this case it becomes permissible to donate it for this purpose.
For more benefit, please refer to Fataawa 82197 and 83172.
Allaah Knows best.