HLA, or human leukocyte antigens, are the proteins that control tissue compatibility. The closer the match, the less risk of a potentially fatal condition called GVHD, or graft-versus-host disease (also known as "rejection"). There is no risk of GVHD when a child receives his or her own cord blood. Within a family, there is a high probability of cord blood matching a sibling or parent, thereby significantly reducing the risk of GVHD. Outside of the family, the situation is much different. HLA antigens are highly polymorphic, with hundreds of different HLA antigens found in the human population (roughly 750,000 possible combinations of three HLA antigens alone). Your best chance of providing a match for your family is to bank your baby's own cord blood.