The fetus has become increasingly accessible and visible as a patient over the last two decades. Two major technical advances have contributed to the obstetrician's ability to study and understand the fetus. The first advance was electronic fetal heart-rate monitoring, followed by the second major advancement in the form of real time ultrasound. Prior to the introduction of these technologies, biochemical determiniations of oestriol and human placental lactogen were used to monitor fetal wellbeing. Currently the emphasis, both in clinical practice and research protocols, is on biophysical surveillance of the fetus.