OBJECTIVE To define the histological lesions in the placenta associated with abnormal blood flow findings and to evaluate their possible clinical significance. METHODS A prospective blind study. METHODS A clinical study at a teaching hospital, Malmö General Hospital, University of Lund, Sweden, morphological studies of placentas being performed at the Institute of Pathology, University of Lausanne, Switzerland. METHODS Thirty-seven pregnancies where intrauterine growth retardation (IUGR) was suspected. METHODS Blood velocimetry of the fetal descending aorta, umbilical artery and vein, and the maternal arcuate artery, using 2.5 MHz pulsed wave Doppler ultrasound. Histological examination of at least five random samples from each placenta. METHODS Frequency of small-for-gestational age (SGA) newborns (birth weight < or = mean -2 s.d.) and of operative delivery for fatal distress. RESULTS Only the presence of placental infarction was significantly associated with IUGR and with intrauterine findings of abnormal blood velocity in the fetal descending aorta and umbilical artery. CONCLUSIONS Placental infarction would seem to be a valuable morphological marker of uteroplacental vascular disease related to IUGR and impaired fetal and umbilical blood flow.