Fetal intrauterine behaviour is not a stable situation but a continuous alternation of states characterized by significant changes in fetal motility, heart rate, hemodynamics, metabolism and response to stimulation. Associations between fetal heart rate patterns and movements occur from 26-28 weeks of gestation onwards. As fetuses grow older these variables become gradually more related temporally and clustered in behavioural states similar to those present in newborns. This article describes the technique of recording and analyzing fetal behaviour, its development in normal pregnancy and its influence on different physiological parameters that are assessed in clinical practice. Furthermore the deviations from the norm occurring in compromised fetuses are described.