The objective of this study was to see if determination of uterine artery velocity waveforms between 20 and 30 weeks in lupus pregnancy and the antiphospholipid syndrome (APS) have a good predictive value for later fetal distress before labor, intrauterine growth retardation, and preeclampsia. Uterine and umbilical artery blood flow velocity waveforms were determined in 21 pregnancies complicated by systemic lupus erythematosus (SLE): 12 with antiphospholipid antibodies (aPL), 9 without aPL. We also studied 7 pregnancies with APS. This retrospective study was running from January 1st 1986 to July 31st 1991, at the Port-Royal Maternity, Paris, France. Abnormal uterine artery blood flow velocity waveforms were found in 10 out of 28 pregnancies at the first examination performed between 20 and 30 weeks gestational age. All the later adverse fetal and neonatal events were predicted by an abnormal uterine artery blood flow velocity waveform. From the 7 cases of fetal distress diagnosed during pregnancy, 6 were predicted by abnormal uterine waveforms and all of these pregnancies resulted in induced delivery before 32 weeks of gestational age. Twelve pregnancies with aPL and normal uterine artery waveforms were uncomplicated. Only 1 out of 7 pregnancies with abnormal uterine artery waveform and aPL ended without complication. Determination of uterine artery flow velocity waveform is a good adjunct to the management of pregnancies complicated by SLE or aPL. This determination has a better predictive value than the presence of aPL.