300 patients at high fetal risk (mean gestational age 34 wk) were randomised to a group for antenatal doppler umbilical artery waveform studies and a control group. The timing of delivery was similar in the control and doppler-report-available groups overall. However, in the report group obstetricians allowed the pregnancies of those not selected for elective delivery to continue longer. There was no difference in the rates for elective delivery (induction of labour or caesarean section) in the two groups, whereas among those who went into labour (induced or spontaneous) emergency caesarean section was more frequent in the control group (23%) than in the report group (13%). Fetal distress in labour was also more common in the control group. Babies from the control group spent longer in neonatal intensive care (level 3) and needed more respiratory support than did those in the report group. The findings indicate that the availability of doppler studies leads to better obstetrical decision making.