[Determination of gestational age by sonar (author's transl)]

For some time it has been recognized that abnormal intrauterine development can lead to dissociation between maturity and external size and/or weight of the fetus. The results of pathophysiological and biochemical studies of fetal growth and nutrition have resulted in attempts to monitor and time every pregnancy at risk. The most recent information in the area of intrauterine development has shown that also organic and functional maturity of fetal organ systems can develop dissociated from gestational age. This observation points out the necessity for additional measures in order to achieve the goals of Planed obstetrics. The possibilities of ultrasound biometry for determining gestational age were presented. Taking normal and abnormal fetal growth and behavior into consideration, the use of ultrasonic diagnostic methods makes it possible to acquire concrete data regarding the size and maturity of some fetal organ systems. The methodological problems such as arise in clinical practice were explained and discussed in light of the most recent developments in equipment.