OBJECTIVE To test whether the introduction of Doppler waveform analysis into the ultrasound department of a tertiary level hospital reduces neonatal morbidity and improves obstetric management. METHODS A randomized controlled trial. METHODS Department of Ultrasound, King Edward Memorial Hospital, Perth, Western Australia. METHODS 505 women with pregnancy abnormalities referred to an ultrasound department for fetal investigation during the third trimester. METHODS Continuous wave Doppler studies of umbilical and uteroplacental arterial circulations. Results were revealed to patients and clinicians. METHODS Principal end point was the duration of neonatal stay in hospital; other end points included the number and type of fetal heart rate monitoring studies, obstetric interventions, frequency of fetal distress, birthweight, Apgar scores and need for neonatal intensive care. RESULTS There was no effect on the duration of neonatal stay in hospital. Small trends in obstetric management were observed with study group patients having fewer contraction stress tests, less likelihood of antepartum fetal distress, and more likelihood of fetal distress after induction of labour leading to emergency caesarean section. Depressed Apgar scores were more frequent in the study group. CONCLUSIONS Introduction of Doppler waveform studies did not result in reduced neonatal morbidity but did have a small effect on obstetric management. For each institution the role of Doppler studies in late pregnancy will be influenced by the usage of other tests of fetal welfare already entrenched in clinical practice.