A baby may be small for a variety of reasons, but there are certain overt maternal and fetal factors which may lead to, or are associated with, a poor fetal growth rate. Pre-eminent amongst the maternal factors is severe pre-eclampsia and in women with this disease the smallness of the baby is almost certainly due to the inadequacy of the uteroplacental circulation. Other maternal factors of importance are cigarette smoking, drug abuse and certain infections such as malaria. The most obvious fetal factors associated with a low birth weight are congenital malformations and chromosomal abnormalities, and there the failure of the fetus to achieve a normal weight is clearly an expression of a generalised disorder of growth and is unrelated to the adequacy or otherwise of the placenta. If cases such as these are removed from consideration, there remains an important residue of unduly small infants who are delivered after an apparently uncomplicated pregnancy, are free from congenital malformations and have a normal karotype; it is this group which is considered here.

Preeclampsia is a common disorder of human pregnancy and is a leading cause of maternal and neonatal death world-wide. The disease is polymorphic, with involvement of the placenta, maternal vasculature, central nervous system, coagulation cascade, liver and kidney. Preeclampsia is also associated with an increased incidence of fetal intrauterine growth restriction (IUGR). Often, the only treatment option is delivery with consequent fetal prematurity. The clinical markers of this disorder include hypertension and proteinuria, which reverse after delivery. Hypertension is a result of the disease and is rarely of pathogenic importance. When accompanied by convulsions the syndrome is termed eclampsia (derived from the Greek eklampsis or “sudden flashing”). A primary clinical goal is to prevent progression to this deadly complication. The incidence of preeclampsia is between 5 and 10% of pregnancies and there is no evidence that this has changed appreciably during the last century. Despite the lack of progress from a practical standpoint, new insights into the aetiology and pathogenesis of preeclampsia continue to arise.

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).