Rhesus blood-free baby Abigail Skinner and mother Natasha play before a news conference at Sydney's Royal North Shore Hospital January 20, 2005. Researchers from the hospital announced they have used preimplantation genetic diagnosis (PGD) to avoid couples having a baby suffering from rhesus factor disease (RhD) a potentially fatal condition caused by incompatibility between a baby's blood and that of its mother.