Although RhD blood group antigens were discovered in the 1930s, haemolytic disease of the newborn (HDN) resulting from RhD isoimmunisation remained a common cause of fetal and neonatal morbidity and mortality for another 30 years. In 1969, routine anti-D immunoprophylaxis was introduced for RhD negative women who had delivered a RhD positive baby.1 This policy was extended in 1976 to RhD negative women who had suffered a miscarriage or undergone a termination, and in 1981 to include women who had undergone other potentially sensitising events (e.g. invasive prenatal diagnosis and other intrauterine procedures). By 1991, neonatal mortality resulting from haemolytic disease had fallen to …