[Ultrasonographic early diagnosis of placenta praevia and its clinical value].

The incidence of early placenta previa amounted to 4 per cent in 4142 ultrasonic screening examinations at 16-20 weeks of gestation. The displacement of the placental edge away from the internal cervical os (migration) was observed in 90 per cent of 158 early placenta previa by prospective study. 86 per cent of the migrations terminated at 28th gestational week. An individual prognostic assessment on the basis of the primary ultrasonic findings cannot be given. The risk of a late abortion was increased (4 per cent). After the migration the rate of the perinatal complications did not change. A second ultrasonic screening scan has already been suggested in the 28th gestational week to select the late migrating and persistent cases and for well-timed performance of preventive treatment. The methodic aspects are discussed. The term placental migration should be used in the ultrasonic nomenclature.