In medicine, in general and fetal medicine in particular, the conceptual development and emerging application of a new diagnostic modality is fuelled firstly by a general recognition of the increasing relative importance of a particular clinical problem and then by critical examination of the body of scientific observation, often disparate in origin, that provides the key insights into the pathophysiology, manifestation and natural history of the disease process. So it is with the evolution of the fetal biophysical profile score. In general terms, until the 1950's the major goal of obstetric care was the prevention of maternal mortality and morbidity. As the result of a host of clinical advances including improved anaesthesia and surgical techniques and availability of blood and blood products, antibiotics and specific other drugs (oxytocin, anticonvulsants, antihypertensives, insulin etc.) maternal mortality declined to the low rates of the present day. Consequently, the focus of obstetric care shifted to the recognition and prevention of death or damage affecting the other patient in the obstetric dyad: the fetus. The first methods for evaluation of antepartum fetal health care were based on measurements of biochemical variables in the maternal compartment (e.g. oestriol, placental lactogen, alkaline phosphatase and oxytocinase).