A pulsed Doppler apparatus was used to assess the blood flow velocity profiles in uterine vessels (arcuate arteries) at 16 to 18 weeks'' gestation to determine if complications associated with impaired trophoblastic invasion of the placental bed (ie, pregnancy-induced hypertension, intrauterine growth retardation, and fetal asphyxia) could be predicted by this measurement. Thirty-one of 126 consecutive pregnancies developed oe or more of the above complications. The sensitivity was 68% and the specificity 69%; the predictive value of a positive test was 42% and that of a negative test 87%. These results seem to represent an improvement over existing predictive techniques. Early identification of such a high-risk group might allow more discerning use of antenatal resources and may lead to new therapeutic measures.