The effect of the amount of amniotic fluid on the form of fetal general movements was studied longitudinally in 19 pregnancies complicated by premature rupture of the amniotic membranes (PROM). Before birth, general movements were studied weekly by means of 1-h ultrasound observations, performed under standardized conditions. In the early postnatal period, 11 of these infants were followed with video recordings of their spontaneous movements. In the fetus, speed and amplitude of general movements were directly related to the reduction in amniotic fluid. A moderate reduction of amniotic fluid was associated with a decrease in amplitude, while a more severe reduction of amniotic fluid caused a decrease in speed as well. Postnatally, the small amplitude and low speed showed a marked tendency to normalize between 1 and 5 weeks. These results are important for the qualitative assessment of motor behaviour in pregnancies with obstetrical complications that are associated with oligohydramnios (such as PROM or intra-uterine growth retardation).